Conditional formatting with VB

Over the past few weeks, i've gotten tons of help from everyone here, thank you all again.

Im working on a project that has been turned over to me, and unfortunately the data in the workbook, is too valuable to get rid of, so i need to keep all the data and the sheet has to be able to be used at anytime so i cant just create a new workbook.

here's my problem, using these forums, i've figured out how to add conditional formatting, some very 'basic' vb coding, and drop down menu's. the problem is that when all the conditional formatting is applied to column ALL of column 'a' and the workbook needs the conditional formatting to carry over to multiple sheets (about 20 in the workbook total) the file size gets really large (about 100 megs) and with the condition of these work computers they have a hard enough time opening them, so i havent applied all the things i want to do.

is there some vb code that i can use that will be a little more efficient?

what i need to do is:

when text is typed into column 'b' i want the aircrafts tailnumber to automatically be inserted into the corresponding column 'a'

as well as, when certain text is typed i want conditional formatting to pick a color and apply it to column 'a' for example...when my coworkers would type in 'nmcmc' in column 'b' i want the corresponding column 'a' to fill red, and when they type 'fmc' i want the corresponding column 'a' to fill green, and 'bq' to fill as 'blue'

like i said, i had applied all those forumals and conditional formatting, however its just too large to apply those 'all the way down' in those columns.

I've attached an example workbook that we are using, its only 1 sheet from the workbook which contains about 20 sheets.

you'll notice, i have implemented a drop down menu in column 'b' as well as made all text typed fill in with all CAPS.

Any help anyone can give me with some vb coding would be greatly appreciated

if anyone needs more info from me, please let me know =)