Image type input question

I have a form that needs to be submitted with an image... and I need the x/y coordinates it sends.

This is not a problem by itself... however, because of the nature of the function it calls, it becomes a problem when brainiac users click on the image repeatedly. This problem does not occur in Firefox; only in IE.

A solution I've used for a similar problem in the same application is to assign the submit button's value to a dummy variable (hidden type), then disable the actual submit button so it can't be clicked again. However, IE ignores the passed x/y values from the image when it is disabled before the form is submitted, and I cannot figure out how to get the x/y values from the image input in javascript.

If anyone has any idea how this can be resolved, please let me know.
Thanks!
-phu