CMDAI,
I think indeed you should maximize your form (DoCmd.Maximize)
Then you can use the property insideheight of Me to know the inner height of the form without the scroll bars and the record selectors.
At that point you can make a calculation based on the heights of each section, that are header,footer,detail, what the height of the subform should be. As the form doesn't have an .height of its own.
regards
Jupiler78