This will return 0 if neither "Express" or "Direct" are entered in D7:

=D3*IF(D7="Express",IF(D3<120, B28,IF(D3<240,B29,IF(D3<420, B30,
B31))),IF(D7="Direct",IF(D3<120,B33,IF(D3<240,B34, IF(D3<420,B35,B36))),0))

You can then take the return value (if it's greater than 0) and deduct the
percentages.

Greg