To select a sound bank on GS Standard instruments you must send controller 0 with the number of the sound bank as the parameter to select the bank, and then send a program change to select the program.
To do this, first put the program change at the beginning of your track. The simplest way to do this is to use the Track Sheet. Click on the Program field in the Track Sheet and a drop-down list box will appear. Select the new program you want. This program change will be entered at the beginning of the track.
Now enter a controller 0 at the beginning of the track. Do this using the Controller Editor. Select Controller 0 from the Data Type list box in the control area of the Controller Editor. Select the Pencil tool and click at the beginning of the track to enter a single controller. Make sure the amplitude of the controller is the number of the bank you wish to select. If you have to edit the amplitude, or move the controller to the beginning of the track in case you entered it incorrectly, use the NSEW, the NS or the EW tools.
Verify in the Event List that you have a controller 0 with the right amplitude followed by the correct program change at the beginning of your track.
Now when you play your piece, the correct sound bank will be selected automatically.