subroutines

Hi all

Iam still confused..ican understand theory wise..when iam trying to implement iam getting lot of doubts..esepcially when passing parameters using USING and CHANGING.i understood the perform part...when we r defining the perfrom using Form iam getting stuck...please is there any other way which can explain me better..the examples given by u's r very good..but i need more clear and easy ones...please.

Thanks and regards

vijaya