Delete formula if cell = 1st entry of specific name

[mm178]

I have a log book for materials used in my Woodworking class. I give the students the 1st sheet of 3/4"ply wood, 1/4" Plywood and 3/4" Particle board, and Melamine. free. Other pieces they have to pay for. I need some thing that looks for the 1st entry with the each name and delete the number from the total column. The Names are provided in a drop down menu so they will all be spelled the same. The student may enter several pieces of each sizes any any order so I can not just not total the 1st 4 items.


Thanks

 

[mm178]

Or that would delete the formula in a cell, rather than the total column