Using Excel 2003-All service packs and updates installed.

I want to allow only certain input and I don't any want drop down lists.

Example 1: Only Yes, yes, Y, y, No, no, N, n are acceptable values. If any
of theses are entered then the cell should display and store either a Yes or
a No only.

Ex 2: Always capitalize the first letter. I can =PROPER(A2) but the data I
actually want fixed or restrict during input is in 500 cells down Column L.

Ex 3: Allow whole numers only. I can Format
CellsNumberCategory:NumberDecimal Places:0 but I can still enter 123.456 .
It will only SHOW 123 but it will actuall store the bad entry of 123.456.

I need help! Thanks.