I am using the standard one. Do I have to edit the prams on the computer and reinsert the card or is there a way to edit on the fly?
The script included in the most recent releases of CHDK now has those values available as parameters that can be set on the fly from the Script menu. You might need to download the latest version - it was only added a couple of weeks ago.
Otherwise, you need to edit the script on your PC and replace the one on SD card with it. CHDK has a crude buit-in text editor that can be used in a pinch on the camera but its a bit of work to understand.