Thanks Doug, I found the 'Confirm conversions on open' box and checked it,
but the behavior did not change. Details: In the 'Mail Merge Helper' dialog,
the second step or button 'Get Data' leads to some options, where I choose
'Open Data Source' and navigate to the multi-sheet workbook and Open it. A
dialog box appears, titled simply 'Microsoft Excel', prompting for 'Named or
Cell Range', with a drop-down list. The only item in the list is 'Entire
Spreadsheet'. I suspect that at this point I could specify the sheet to be
used (by typing over 'Entire Spreadsheet' with my selection), but I don't
know the syntax for specifying the sheet name. I think it may be the sheet
name either preceeded by, followed by, or surrounded by exclamation points; I
have tried several combinations but it always insists on using the data from
the first sheet (the one represented by the leftmost tab) of the workbook.