Validation Rule Help

Hey guys,
I am trying to set a validation rule on MS Excel 2010 that only lets you enter a certain pattern of characters.
The data I am trying to enter in are ID numbers, for example AA101 E.
The general pattern to be: Letter, Letter, Number, Number, Number, Space, Letter

Can anyone tell me how I do this?

Thanks in advance.

On a worksheet make a list of the pattern for instants:

WORK ID@S
AA101E
AA102F
AA103E
AA104R

Highlight the ID Codes (In Bold)

In the top left corner name the Cells (ID)

Highlight the column inwhich you want the validation.

Go to Data/ Validation/ Choose List/ enter =ID in ref box at the bottom.

Click OK

I have done this, but I can't enter anything in!

And also, if I want to make like over 100 ID numbers, will I need to list them all, highlight them and do it manually?

Yes create your list Unless you can copy and paste from somewhere.

You need to name your list by highlighting them and giving the cells a name in the top left corner.

Once this has been done

Highlight the cells were you want a drop down menu

Data/ Validation/ List/ in the bottom row you need to put =(name of cells)

Ok