The file overwrite warning probably comes from Excel. Before the close try:
objExcel.DisplayAlerts = False
I don't have time to find out, but I think your merge needs something like:
.ActiveDocument.Mailmerge.OpenDataSource "C:\merge.xls![Sheet1]",,,false,true
In other words, specify the sheet in the data source. Another option could be to delete the extra worksheets in Excel before you close the file. I think if Excel has only one worksheet it knows where to go for the data.
Of course you might try skipping the whole output to Excel and use a query in Access as your data source. Of course that depends on whether your Excel output is more than just a simple query. Not sure the syntax for that but it might be as simple as:
.OpenDataSource CodeDB().Name & "![queryname]" ???
You could record a macro in Word to get all of the proper commands to copy (and update as appropriate) in your Access code. That's usually the way I figure out what I need.
Randall J Weers
Membership Vice President
Pacific NorthWest Access Developers Group
http://www.pnwadg.org