Trouble to record pgm change

Hi,
I'm, dealing with a problem in programs.
I have two identical programs in my 2k classic and in one of those I have made a little difference in low pass filter. I have a long sequence and at a specific bar I want to change from one program to another but I can't, the sequence still plays the same. At step edit in the sequence there's a function which says "program change". Do you have any idea how this is gonna help or even if this has anything to do with the problem I'm dealing with?
Any help appreciated
Thanks in advance

Nice tip.
I find the solution though. In step edit-->program change and press insert with one of the f buttons. It shows up a highlighted area which you can select which pgm will play at a specific time.