>>>Easy :-)
>>>You just need to join two table by Trucks.Overweight BETWEEN MinWeight AND Maxweight
>>>And then to sum that additional column to (Trucks.Overweight - MinWeight + 1) * FineRate
>>>
>>>Something like this (NOT TESTED!!! and all in T-SQL, sorry)
>>>

>>>DECLARE @Truck TABLE (id int, overweight int);
>>>insert @truck values (1,3500);
>>>insert @truck values (1,2500);
>>>insert @truck values (2,1500);
>>>insert @truck values (2,500);
>>>insert @truck values (1,500);
>>>
>>>DECLARE @ttt table (minweight int, maxweight int, fineamount numeric(8,4), PreviousAmount numeric(8,4));
>>>insert @ttt values (   1,     1000,0.005, 0)
>>>insert @ttt values (1001,     2000,0.01 ,1000*0.005)
>>>insert @ttt values (2001,     3000,0.015,1000*0.005+1000*0.01)
>>>insert @ttt values (3001,     4000,0.02 ,1000*0.005+1000*0.01+1000*0.015)
>>>insert @ttt values (4001,     5000,0.025,1000*0.005+1000*0.01+1000*0.015+1000*0.02)
>>>insert @ttt values (5001,999999999,0.03 ,1000*0.005+1000*0.01+1000*0.015+1000*0.02+1000*0.025)
>>>
>>>SELECT Truck.*, TestMe.PreviousAmount + (Truck.overweight-TestMe.minweight+1)*fineamount AS Something
>>>FROM @Truck Truck
>>>INNER JOIN @ttt TestMe ON Truck.overweight BETWEEN TestMe.minweight AND TestMe.maxweight
>>>

>>>
>>
>>The inner join condition is incorrect in this code, but the idea is good....
>
>
>Why?

Because of BETWEEN you're using. You need to use > MinWeight as George did.