Material calculating cross refrence formula

Hi, I am trying to write a program that will calculate my material totals. I am in marine construction, so I am totalong lumber and bolts ect.. I can do the math perfectly by counting parts ,but this is too time consuming.
so this is where I am stuck: I have a legnth row starting with B5 through B51 each cell will represent a legnth, starting with 4 and ending with 50. In columns A 5 through V5 are set aside to count the many diffrent materials, to later tally.
Next I have a width row, starting with B54 through B77. representing 2 foot through 24 ft. .
in B203 I want to type the legnth, and in B204 I want the width.
If I type 32 into cell B86 and 4 into cell B87, it should cross refrence to cell B86 for the legnth and B87 for the width. Now I have gotten that problem, but I keep getting the formula wrong when I try to tie tts many diffrent widths.into each legnth cell.
also I am able to tie all the material into this cross reference. I am just hurting on the cross reffrence tie with variations.
Any help would be greatly appreciated. Thanks for listening.

I am confused to what the outcome is supposed to be after entering those two items and why?

I am more than confused. I really don't understand the structure of the workbook or what you are trying to do with it.

Regards