Your welcome.
It just occurred to me that if it is ship production you want to stop, you can set all ships in the shiplist that you don't want to appear as "R" in the Special Role column. They will not appear anywhere after that. Be warned though, if the mission calls for that specific ship to appear it will probably crash.
Another thing you could try is setting the Year First Available to 999 for all ships you don't want around. The missions will generate them if needed (I'm assuming the campaign here, normal "Conquest" missions don't usually call up particular ships).