Dont worry Ram we have all been there before.
I use a caliper when I build kits, I go through and measure all my screws and place them in little bins (Microwave dinner trays).

Tower sells a kit that has like a ton of screws in it for the hobby stuff. I have thought of getting one many times just to have in the box. I dont have a link at the moment but I know tower has it. Check it out when you get a chance.

Dbow