I'm thinking it might be possible with managed code, but not with script languages. Reason being that you'd have to use threads to run a real-time "clock" in the background to determine when 5 minutes have passed.
The only other idea I would have is putting an onBeforeChange() on the root element and check the system time every time it fires. This would work pretty well if the form was being worked on (it would be an estimate not 100% accurate), but if the form was just sitting idle it wouldn't work at all.
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Matt Faus
InfoPath Dev Texas
Matt Faus / Microsoft InfoPath MVPQdabra® Software / Streamline data gathering to turn process into knowledge