Ask user for decision action

Hi.
I'm currently trying to find out how to implement a rules, where at some point during its run the user should be asked for a decision.
A simple Yes/No would be enough.

For a start it would be enough to have the user decide whether to execute ther rule at all or not (which means, that this could be an outside process).

Nevertheless I would also need this during the execution of a rule.

How can I achieve this?

Thanks for any help.
--udo.