Mel,
In the FRX the values are in 10,000th of an inch or 1000th of a centimeter. If you want to add an offset and you want it in inches then multiply your offset by 10,000. So for .25 inches (1/4 inch) you would need to multiply .25 * 10,000 to add to the VPOS or HPOS. There is no limit that I am aware within the width or height of the page. It just won't get painted onto the page it will be off of the printable DEVICE CONTEXT area.