Add File to Existing Object

I managed to get it working this way, hopefully that might help others.

Option Explicit

' This is mandatory to be able to add files, otherwise exception will raise.

Dim oCheckedOutFiles: Set oCheckedOutFiles = Vault.ObjectFileOperations.GetFilesForModificationInEventHandler(ObjVer)

' Special folder value for TemporaryFolder, from https://msdn.microsoft.com/en-us/library/a72y2t1c(v=vs.84).aspx.
Const TemporaryFolder = 2
    
' Create a filesystemobject to help working with files.
Dim objFSO: Set objFSO = CreateObject("Scripting.FileSystemObject")

' Get a reference to the temporary folder.
Dim strTempFolderPath: strTempFolderPath = objFSO.GetSpecialFolder(TemporaryFolder).Path

Dim oTemplateObjects: Set oTemplateObjects = GetTemplateObjects()
Dim oTemplateObject
For Each oTemplateObject In oTemplateObjects
	
    ' Get the files for the current objver.
	Dim objFiles: Set objFiles = Vault.ObjectFileOperations.GetFiles(oTemplateObject.ObjVer)
 
    
	' Create our collection to return.
	Dim objSourceFiles: Set objSourceFiles = CreateObject("MFilesAPI.SourceObjectFiles")
 
	' Iterate over the files and download each in turn.
	Dim intCounter, objFile
	For intCounter = 1 To objFiles.Count
		
		Set objFile = objFiles.Item(intCounter)
	
		' Full download path including the file name and extension
		Dim strTemporaryFilePath: strTemporaryFilePath = objFSO.BuildPath(strTempFolderPath, objFSO.GetTempName()) & "." & objFile.Extension
 
		' Download the file.
		Vault.ObjectFileOperations.DownloadFile objFile.ID, objFile.Version, strTemporaryFilePath

        ' Upload the file to the object 
        Vault.ObjectFileOperations.AddFile ObjVer,objFile.Title,objFile.Extension, strTemporaryFilePath

	Next

Next

Function GetTemplateObjects()

    ' Search for Template having the same class.
    Dim oSearchCondition : Set oSearchCondition = CreateObject("MFilesAPI.SearchCondition")
    Dim oSearchConditions : Set oSearchConditions = CreateObject("MFilesAPI.SearchConditions")

    ' Class = Credit Committee Meeting 69
    oSearchCondition.ConditionType = MFConditionTypeEqual
    oSearchCondition.Expression.DataPropertyValuePropertyDef = MFBuiltInPropertyDefClass
    oSearchCondition.TypedValue.SetValue MFDatatypeLookup, 69
    oSearchConditions.Add -1, oSearchCondition

    ' Is template = True
    oSearchCondition.ConditionType = MFConditionTypeEqual
    oSearchCondition.Expression.DataPropertyValuePropertyDef = MFBuiltInPropertyDefIsTemplate
    oSearchCondition.TypedValue.SetValue MFDatatypeBoolean, True
    oSearchConditions.Add -1, oSearchCondition

    oSearchCondition.ConditionType = MFConditionTypeEqual
    oSearchCondition.Expression.DataStatusValueType = MFStatusTypeDeleted
    oSearchCondition.TypedValue.SetValue MFDatatypeBoolean, False
    oSearchConditions.Add -1, oSearchCondition

    ' Invoke the search operation.
    Set GetTemplateObjects = Vault.ObjectSearchOperations.SearchForObjectsByConditions(oSearchConditions, MFSearchFlagNone, false)

End Function

I managed to get it working this way, hopefully that might help others.

Option Explicit

' This is mandatory to be able to add files, otherwise exception will raise.

Dim oCheckedOutFiles: Set oCheckedOutFiles = Vault.ObjectFileOperations.GetFilesForModificationInEventHandler(ObjVer)

' Special folder value for TemporaryFolder, from https://msdn.microsoft.com/en-us/library/a72y2t1c(v=vs.84).aspx.
Const TemporaryFolder = 2
    
' Create a filesystemobject to help working with files.
Dim objFSO: Set objFSO = CreateObject("Scripting.FileSystemObject")

' Get a reference to the temporary folder.
Dim strTempFolderPath: strTempFolderPath = objFSO.GetSpecialFolder(TemporaryFolder).Path

Dim oTemplateObjects: Set oTemplateObjects = GetTemplateObjects()
Dim oTemplateObject
For Each oTemplateObject In oTemplateObjects
	
    ' Get the files for the current objver.
	Dim objFiles: Set objFiles = Vault.ObjectFileOperations.GetFiles(oTemplateObject.ObjVer)
 
    
	' Create our collection to return.
	Dim objSourceFiles: Set objSourceFiles = CreateObject("MFilesAPI.SourceObjectFiles")
 
	' Iterate over the files and download each in turn.
	Dim intCounter, objFile
	For intCounter = 1 To objFiles.Count
		
		Set objFile = objFiles.Item(intCounter)
	
		' Full download path including the file name and extension
		Dim strTemporaryFilePath: strTemporaryFilePath = objFSO.BuildPath(strTempFolderPath, objFSO.GetTempName()) & "." & objFile.Extension
 
		' Download the file.
		Vault.ObjectFileOperations.DownloadFile objFile.ID, objFile.Version, strTemporaryFilePath

        ' Upload the file to the object 
        Vault.ObjectFileOperations.AddFile ObjVer,objFile.Title,objFile.Extension, strTemporaryFilePath

	Next

Next

Function GetTemplateObjects()

    ' Search for Template having the same class.
    Dim oSearchCondition : Set oSearchCondition = CreateObject("MFilesAPI.SearchCondition")
    Dim oSearchConditions : Set oSearchConditions = CreateObject("MFilesAPI.SearchConditions")

    ' Class = Credit Committee Meeting 69
    oSearchCondition.ConditionType = MFConditionTypeEqual
    oSearchCondition.Expression.DataPropertyValuePropertyDef = MFBuiltInPropertyDefClass
    oSearchCondition.TypedValue.SetValue MFDatatypeLookup, 69
    oSearchConditions.Add -1, oSearchCondition

    ' Is template = True
    oSearchCondition.ConditionType = MFConditionTypeEqual
    oSearchCondition.Expression.DataPropertyValuePropertyDef = MFBuiltInPropertyDefIsTemplate
    oSearchCondition.TypedValue.SetValue MFDatatypeBoolean, True
    oSearchConditions.Add -1, oSearchCondition

    oSearchCondition.ConditionType = MFConditionTypeEqual
    oSearchCondition.Expression.DataStatusValueType = MFStatusTypeDeleted
    oSearchCondition.TypedValue.SetValue MFDatatypeBoolean, False
    oSearchConditions.Add -1, oSearchCondition

    ' Invoke the search operation.
    Set GetTemplateObjects = Vault.ObjectSearchOperations.SearchForObjectsByConditions(oSearchConditions, MFSearchFlagNone, false)

End Function