That's not going to happen without a lot of effort. A mailmerge can only work with a single data source - in this case a single worksheet. Besides which, it's not apparent what the purpose is behind having different worksheet names in column C when both sheets appear to be in the same workbook.

What is the problem with a having different mailmerge main document for each data source?

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Cheers,
Paul Edstein
[Fmr MS MVP - Word]

Thank you for your reply,

The problem is the main data source has well over 50+ worksheets, which would mean you would need to have 50 separate files, which points to the right worksheet for each separate client.. (and counting as more clients come along), this of course can be achieved, creating all those files, but its not ... shall I say, a elegant solution to the problem...

But I completely agree, this is a huge monumental task or some real wizardry VBA script needed, to which I have no idea how to do...

In any case, thank you for taking the time to reply.

Regards,
Val