Conditional formatting a mail merge

I am currently trying to create a mail merge that uses peoples name in the main body of text i.e.

Please return Mike Wazowski's name badge to the front desk.

My problem is that if a name ends with an s grammatically all i need is the apostrophe. Is there a way with conditional formatting (or some other type of Excel wizardry) for Excel or the mail merge to recognise whether the cell value ends in an s?

Yours,

An Excel muggle.