macro to change the format of cells once pasted

hi all,

can someone help me on my problem..

I have a data in column A like ,7,9,181,78,100

What i need to is to change the format if the data pasted in column a1 = 7, it should be change to 007,
if 78 then should be 078.

Hope you can help me..

You can just format your Column A to Custom 000.

format-cells.png