Source: MultiCHAX User Security
Change the default control for a MultiCHAX user
You can change the default control for a MultiCHAX user within the MultiCHAX.exe program by going to SETUP > Maintain Users.
Highlight the user you wish to make changes to and select "Update User"
Click on the "Change Default Control for this User" button
Double click on the control you wish to use and make it the default, then click OK to continue.