How to edit a cell by pasting additional content?

I am a newbie to macros. I've tweaked a couple that others have written, but haven't composed my own.

I have a long column of numbers; 1, 2, 3, . . .
I want to add the string "Gage_" in front of each number in the column so that I will have; Gage_1, Gage_2, Gage_3, . . .
I'm looking for a way to add this quickly in Excel 2007.

Thanks for the help.

Phil