VBScript - Click Handler For Form Button?

[User 2392]

How exactly do I add a click handler for a button on a form using VBScript? In Java it's I want to call a subroutine before the form does its POST thing. Or, can the ACTION of a form be set to execute a VB sub instead of going to an URL or script?

[jburrow]

    sub beforeload()
            msgbox "Hello World"
    end sub