Sorry about the false start, I've now had a play about, and got a working sample!
Sub iPartAccess()
On Error Resume Next
Dim xlDocName As Excel.Workbook
Dim oiPartFactory As iPartFactory
Dim xlWS As Excel.WorkSheet
Dim xlApp As Excel.Application
Dim odoc As PartDocument 'Dim odoc As AssemblyDocument (for iAssemblies)
Dim xlName As String
Set odoc = ThisApplication.ActiveDocument
Set xlApp = CreateObject("Excel.Application")
xlApp.Visible = True
If odoc.ComponentDefinition.IsiPartFactory Then
Set oiPartFactory = odoc.ComponentDefinition.iPartFactory
xlName = oiPartFactory.ExcelWorkSheet.FullName
End If
Workbooks.Application.Visible = True
End Sub
This will open the embedded xl sheet outside inventor (but the iPart must be open). There is probably a way to open the xl sheet using Apprentice, but i'm not sure so don't quote me on this.
Anyway, you can make any changes you need in the sheet, and c&p values to other workbooks as required, but remember to change any changes when you close it.
I'm not sure why, but if you delete the xlName line, or the "Workbooks.Application.Visible = True" line, the code doesn't work. Also if you run the code twice you will notice that the file name is different (it opens as a temp file, and as such is assigned a new code each time (I think)).
If you need any more help, I will do my best to help you.
Cheers
Jon