Calculator needed

I'm using Excel 2003 and need a little help creating a "calculator" for the guys in my workshop to use. It needs to be simple to use as none of us are experts in Excel.
Basically I have two lists of components, a component from List A is added to one from List B and a total in £'s needs to be shown, simple enough I hear you say HOWEVER the LENGTH of component B is variable.
For example
Input part # ABC in A1 and £50 is shown as a total in D1, then input part # 123 in B1 and the length of 100 in C1 and the total changes to £100. Then if you change the figure to 200 the total changes to £150

Any help would be appreciated it it's possible to do this?