i have a problem say

i have three files

1.costcatelogue 2. logical item 3. tax

logical_item , tax logical item, tax category tax category ,taxvalue


so each files have two two columns and the condition is as follows:-

tax column of costcatelogue has to be filled with taxvalue of tax file.

i order to do this we need to do following:-
1.check the logical item name logical item file and pick the tax category .
2.match the tax category into tax file and pick the tax value and fill into tax field of cost catelogue.

but i dont know how?

can anybody help me please.

as i am very much new to excel .

thanks in advance.