Macros

Hello,
I need to copy paste data between 2 excel files. I need to do this same kind of copying & pasting between different pairs of excel files.
I created a macro between one such pair and saved it in 'Personal.xls'. But then when I try copying & pasting between a different pair of similar excel files, the macro keeps asking for the files I used for creating the macro and does not do the task for this pair of excel files. Help!