I'd like to call a sub when the lowercase t is entered in any cell in Column-A. If I were to try and type "Bottom" in cell A2, as soon as the third character (the "t") was typed then a sub would be called where I could perform other operations. If in cell B2 (or any cell not in Column-A) I would be allowed to type "Bottom" without any actions being called.

How can I accomplish this?

Thank you in advance,
Andrew