Try the MoveSize method in the form's Open event. See VBA Help for more
information. It would be something like this for your 10x20 form (big
screen?) that opens at the top left corner:
DoCmd.MoveSize 0, 0, 20 * 1440, 10 * 1440
For the form in the center of the screen, you will have to experiment to
find the right measurements for the first two numbers. Maybe something
like:
DoCmd.MoveSize 2 * 1440, 1440, 10 * 1440, 10 * 1440
The reason for the 1440 is that the measurement unit is a twip, which is a
20th of a point, of which there are 72 per inch. Multiply the desired
number of inches by 1440 as shown, or just multiply inches by 1440:
DoCmd.MoveSize 0, 0, 28800, 14400