If you want to do it in BO check out
this You don’t say what version of BO you have but I know this works in V5. It should do exactly what you need.
ken.gaul 
(BOB member since 2002-06-18)
If you want to do it in BO check out
this You don’t say what version of BO you have but I know this works in V5. It should do exactly what you need.
ken.gaul (BOB member since 2002-06-18)