Something like this would probably suffice, kind of a hack fix though.
PHP Code:
//#CLIENTSIDE
// Usage: getMaxScrollPos(someScrollGUI);
// Returns: {maxhorizontalpos, maxverticalpos}
function getMaxScrollPos(obj) {
// Record Original Scroll Position
temp.original = obj.scrollpos.tokenize();
// Scroll to the Limits
obj.scrolldelta(0x7fffffff, 0x7fffffff);
// Record Actual Limits
temp.max = obj.scrollpos.tokenize();
// Scroll back to Original Position
obj.scrollto(temp.original[0], temp.original[1]);
// Return Actual Limits
return temp.max;
}