Gravity

[MidgetsBro]

How can I make a ball bounce up and down on a line at the bottom of my form, and look like it's realistically bouncing? I know I will have to do somthing with gravity, but I don't know exactly how to do it. I am using this to define my ball area:

Type UserObject
     top as long
     left as long
     bottom as long
     right as long
End Type
Dim Ball as UserObject

I don't know what code I need to put in a loop, or even how to structure it. Eventually I want to make a sort of volleyball game, but for now I just want to make a ball bounce.

Thanks
-Joey