having the 'Freeze Window' script step at the beginning of your script could do the job....
Freeze window would be my first suggestion but I find Freeze Window to be one of the more frustrating script steps in FileMaker. At times it does what you expect but other times it doesn't seem to do anything. It also seems that the behavior sometimes changes from version to version. If it works, problem solves. If not you can try to update the other layout from the layout that you are on. You can place portals and related records in the dead space on the right side of the layout that you can use to update tables. A portal that allows creation of new records can be used to create records in another table. Set field can also be used to create records in another table. Hopefully the Freeze Window will work but there might be other options if not.
If the fields you are updating are related to the table you are in, (or you can create a relationship to it) them put them off to the right hand side of the layout , even in a portal and set them on the current layout so you don't actually go anywhere..
Also can make this transactional so that if anything goes wrong then all changes can be fooled back.
Set Field By Name is also your friend here..
Open a new window off screen is another method sometimes used.