Counter Macro On Image Click

Hey everybody.

I wanted to add a counter macro where when a certain image is clicked on my spreadsheet, it will add 1 or take away 1 number in a specified cell on my spreadsheet.

For instance, if my cell A1 had the number 0 in it, and I had 2 images beside it (a "+" and a "-"), when the "+" image is clicked, I need it to add 1 to cell A1, making it 1, and vice versa if clicking the "-" image for -1. I want it to be cumulative, so every time you click "+", the number in A1 will increase to 1, 2, 3, 4, etc, and same with the "-" making it -1, -2, -3, -4, etc.

If anybody could help with this, it would be greatly appreciated.


Other Info:

I'm using Excel 2007
I have no knowledge on how to program macros, so I may need some step-by-step instructions :P