Hi Stephen
Yes this is possible.
Firstly you need to write a Word Macro that opens an instance of Excel and the document that contains the data you want to read.
Once you have done that then to find the last row of data in an Excel sheet use this line of code:
LastRow = ActiveSheet.UsedRange.Rows.Count
You can then add the code to do your MailMerge.
Hope this helps.
Good luck.
Tony(OTPM)