Avoid form Re-Submit

I’m developing ASP.NET applications and stuck with a “problem” relating to resubmit behaviour.
I’m controling the re-submit using a counter in form submit event which disables the submit if it’s already been posted.
My application is a 3 step workflow and when the 3rd step is shown the transaction was submited from step2 to step 3.
What’s my problem? Well… i want to avoid the user to resubmit the data by pressing the F5 or all other possibility. I don’t want to disable the key because may be workarounds.
I’m wondering if i can remove the post data in a HTTP module that runs after the render was completed and right before the response is sent to the user.