Using IF function or similar function

I have to make excel sheet for steel weight record which transport using 4 different trucks and truck numbers and their empty weights are as shown

Truck No Empt. Wgt. (Kg) Truck No Empt. Wgt. (Kg) Truck No Empt. Wgt. (Kg) Truck No Empt. Wgt. (Kg)
LY-3618 15300 LY-4098 17290 LY-3486 13470 LY-2974 13010

Date Location Truck No. Ticket No. weight with Steel Weight of Steel


I have empty truck weight and weight with steel . So i want to fill weight of steel column ( weight of truck with steel - weight of empty truck ) for this , I need formula to weight of steel column when i enter truck number and weight of truck with steel the formula should calculate deducting relevant weight of empty truck

example
if I enter LY-3618 weight of steel should calculate deducting 15300 kg from truck weight with steel xxxx kg ( xxxxkg - 15300 = yyyy kg
if I enter LY-4098 formula should calculate truck weight with steel www kg - 17290 kg = zzzzkg

Please help thank you