Programmatically Remove Mailmerge Data Source using VB.NET - excel

Question

Working on automating a mail merge using Excel as the data source and merging into multiple .doc files as templates.
The first pass works great! Here is an outline of how the code is supposed to work:
1) Data is pulled from SQL Server into Excel and saved as .xlsx on a network drive.
2) Excel sheet is attached as a datasource to the .doc file and the merge is executed successfully.
3) xlWorkbook.Close(), xlApp.Workbooks.Close(), and xlApp.Quit(). Then I call my garbage collection routine to release the COM objects using Marshal.ReleaseComObject, and it appears Excel closes properly.
4) Use the same Excel source file with different template to create the next batch of letters.
At this point it seems the Excel file isn't releasing from memory after previously being used as a datasource. When I use wdAffDoc.MailMerge.OpenDataSource, I get a popup window from Word asking me which table to use and the list of tables is blank. The source data spreadsheet is NOT listed in the "spreadsheet" window of the popup. Last time I had this issue it was because I had the source file open on a different machine, and it wouldn't merge due to the lock. When this code bombs out, I look in Task Manager and see 1 or sometimes 2 entries of "EXCEL.EXE *32" listed under my username. The code will not run until the remaining EXCEL.EXE *32 processes are terminated.
Looking for any input as to the direction I should go here. Should I suspect my garbage collection routine, or do you think it's something else?
Here is my garbage collection:
Public Sub releaseObject(ByVal obj As Object)
Try
System.Runtime.InteropServices.Marshal.ReleaseComObject(obj)
obj = Nothing
Catch ex As Exception
MsgBox(ex.Message)
Finally
GC.Collect()
End Try
End Sub
Here is the first pass after pulling the source data (works as expected):
frmPleaseWait.Label1.Text = "Now merging documents. Please wait."
frmPleaseWait.Refresh()
Dim wdApp As New Word.Application
Dim wdDoc As New Word.Document
'Select template based on Queue chosen
If Queue = "716" Then
wdDoc = wdApp.Documents.Open("X:\Admin\LEGAL\MERGE LETTERS\UPH Vfn 2 Def.doc")
End If
wdApp.Visible = False 'Set this to False before going live -- true for debugging
wdDoc.MailMerge.OpenDataSource(Name:=fileDest, SQLStatement:="SELECT * FROM [Sheet1$]") 'Add a WHERE clause for filtering for affidavits, etc.
'.Destination 0 = DOCUMENT, 1 = PRINTER
wdApp.ActiveDocument.MailMerge.Destination = 0 'send to new document
With wdApp.ActiveDocument.MailMerge.DataSource
.FirstRecord = 1 'wdDefaultFirstRecord
.LastRecord = -16 'wdDefaultLastRecord
End With
wdApp.ActiveDocument.MailMerge.Execute(Pause:=False)
wdDoc.Close(SaveChanges:=False) 'Close the original mail-merge template file
wdApp.ActiveDocument.SaveAs2(savePath & "\" & ProcessDate & " " & Queue & " Verifications.doc")
wdApp.Quit()
wdDoc = Nothing
wdApp = Nothing
And here is the second (offending) pass:
Dim wdAffApp As New Word.Application
Dim wdAffDoc As New Word.Document
If Queue = "716" Then
wdAffDoc = wdAffApp.Documents.Open("X:\Admin\LEGAL\MERGE LETTERS\Suit Affidavit 2 Def.doc")
End If
wdAffApp.Visible = False 'Set this to False before going live -- true for debugging
'****************THIS IS THE LINE THAT PRODUCES THE ERROR****************
wdAffDoc.MailMerge.OpenDataSource(Name:=fileDest, SQLStatement:="SELECT * FROM [Sheet1$] WHERE [Suit_Bal] >= 5000") 'Add a WHERE clause for filtering for affidavits, etc.
'************************************************************************
'.Destination 0 = DOCUMENT, 1 = PRINTER
wdAffApp.ActiveDocument.MailMerge.Destination = 0 'send to new document
With wdAffApp.ActiveDocument.MailMerge.DataSource
.FirstRecord = 1 'wdDefaultFirstRecord
.LastRecord = -16 'wdDefaultLastRecord
End With
wdAffApp.ActiveDocument.MailMerge.Execute(Pause:=False)
wdAffDoc.Close(SaveChanges:=False) 'Close the original mail-merge template file
wdAffApp.ActiveDocument.SaveAs2(savePath & "\" & ProcessDate & " " & Queue & " Affidavits.doc")
wdAffApp.Quit()
wdAffDoc = Nothing
wdAffApp = Nothing
'Signal the end
frmPleaseWait.Dispose()
MsgBox("Mail merge complete")

Answer 1

Apparently my code worked!
After reviewing further, I discovered there was still WINWORD.EXE *32 running in the task manager. When I switched to that application, a popup window asked me if I wanted to save or delete the recovered files... must have been an error from one of my prior runs that got stuck in memory. Once I told Word to drop the recovered files, the code completes as expected. Whew! Glad this one is solved!