Sorry. Should have used your variable names ...
Code:
big_number[0] = in_high * 10000
big_number[1] = R0
big_number[0] = big_number[0] + in_low
IF (big_number[0] < in_low) THEN big_number[1] = big_number[1] + 1
Just stick it after the HSERIN.

P.S. Nice "Colors".