>I have a procedure that I want to execute every time a webapp starts.
>The snag is that I want it to execute only once, even if there are for example 4 processes in the minimum pool.

If you have a minimum pool, this is the same as looking for something that executes when the webapp server starts.
It's a workaround, but you can make a second webapp with a single process in the pool (min pool = 1 and maxpool = 1) that does what you need when it is started.