Lead Lifetime Report

Hello

I posted this question in Salesforce help and was pointed in this direction for help.
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"Lead Lifetime Report

Bit of an issue with the report. If one of my guys creates an additional opportunity after conversion and closes that opportunity, there is a break in the lifetime report and the lead will remain neglected although there has been a closed won. How do I?:

1 - Update the 2nd opp to be included in the report.
2 - Stop my guys creating another opportunity until the original is closed.
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I'm looking for a trigger that stops an additional opportunity being created if another is owned by the user and is still open.

Any help or advice will be appreciated.

Marc