I am having a problem trying to do a mail merge from an Excel macro.

I am not able to specify whick sheet the merge should use. can anyone give me a hand on this?

Here is what I am doing:
MailMerge:
fname = ("\\fileserve\Timetndr\Service Level\Tommy Nobis\Thank You Letter." + InputDate + ".doc")
Dim appWd As Word.Application
Dim WdDoc As Word.Document

Set appWd = CreateObject("Word.Application")
appWd.Visible = True
On Error Resume Next

On Error GoTo 0

With appWd
Set WdDoc = appWd.Documents.Open("\\fileserve\Timetndr\Service Level\Tommy Nobis\Report Templates\Thank You Letter.doc")
WdDoc.Activate
WdDoc.MailMerge.OpenDataSource Name:="\\fileserve\Timetndr\Service Level\Tommy Nobis\Data Files\Thank You Letter.xls", _
ReadOnly:=True, LinkToSource:=0, AddToRecentFiles:=False, _
PasswordDocument:="", PasswordTemplate:="", WritePasswordDocument:="", _
WritePasswordTemplate:="", Revert:=False, Format:=wdOpenFormatAuto, _
Connection:="", SQLStatement:="", SQLStatement1:=""
With WdDoc.MailMerge
.Destination = wdSendToNewDocument
.SuppressBlankLines = True
With .DataSource
.FirstRecord = wdDefaultFirstRecord
.LastRecord = wdDefaultLastRecord
End With
.Execute
End With
ActiveDocument.SaveAs fname
End With
WdDoc.Close
Set WdDoc = Nothing
Set appWd = Nothing