how should I write if function here to have if the in stock is enough it calculates cost unit *units, if not =0.how should I write vlook up if the in stock is enough? In stock is in other sheet and I just wanna general formula.

DIRECT MATERIALS Req.No. Item Code Details/Description Quantity Cost/Unit Amount 223 M1021 MGX 8025 Chip Set 3 110.90 121) 224 R1004 Robot Kit 38G 3,288.90 228 R1024 Relays - Medium Pack 274.80 225 51009 Servo Motors B21 (4 pack) 1,051.20 225 $1010 Servo Motors A21 (8 pack) 1,995.00 225 S1014 SMC Pneumatic Part X-33 Of W W W W 748.60