I've attached an excel file of what I need.

Basically, I need help figuring out a way that I can click on an entire column, identify all the duplicates and add _1, _2, _3, and so on after each duplicate.

For example, if the number 1234 shows up 4 times in column A I want to be able to click column A and through a series of functions change it to say 1234_1, 1234_2, 1234_3, 1234_4.

I hope that makes sense! Thanks any advance for the help.