Terminating workflow during MetadataCapture task

System

TS 6.1 Win2K

In my workflows, Metadata Capture is the first task.
When the user enters submit comments, it is possible for him to click on the submit button more than once before the workflow is started.
Because of this, my metadata capture task is getting started multiple times.
Now if the user wants to remove the reduntant task, there is no way for him to delete it unless he asks the Master to do it for him.

I'm planning to add a timeout in Metadata capture task.
Is there any better way of handling this?
Is there any way to disable multiple clicks of submit button?

TIA