Excel Macro

Please! If someone knows, mail me: dcyrillo@ig.com.br

I need to do a button with a macro, that when the user click in this button,it's save the document in a file called 001_1.xls, 001_2.xls...where only the number 1, 2 will change, but i will make this change, when prompts to me save file as... Summarizing: I want that the document, when i click in the button, prompt the pop save file as... but preserving the number 001_ before...
Please help me....Thanks...