Since the RSQ function is looking for 2 ranges...
You may need to use this approach
(untested....we don't have your data):
=RSQ(IF((Sheet1!$B$5:$B$500>Sheet2!L$1)*(Sheet1!$B$5:$B$500<=Sheet2!L$2),
Sheet1!F5:F500),IF((Sheet1!$B$5:$B$500>Sheet2!L$1)*
(Sheet1!$B$5:$B$500<=Sheet2!L$2),Sheet1!G5:G500))
Does that help?