See msgbox function in vb help.
There are several optional arguments for the function.
msgbox("Would you like to run the macro?",vbyesno,"Run Macro?")
Will give you a message box with two buttons. If the person clicks yes, then the function will return the integer 7. So you need an if statement that looks like this:
If msgbox("Would you like to run the macro?",vbyesno,"Run Macro?")=7 then
Call RunMacro (or something to call the procedure of the macro). The help menu for this function is very useful and will let you know what other buttons you can add.
Dave