Custom Buttons In MS Outlook 2003

[ISUTri]

Hi, I'm trying to place a custom button in Outlook 2003 that calls some VBA code (that automatically detach's files to a certain folder). Problem is I can't find where to call the file within outlook. I can do it within MS Access (Custom). What can i do? Is there anyway I can program it so the code runs whenever I get new mail? Or will that slow it down too much?

Thanks for your help!