Data validation to keep a prefix

I am creating a budget tracker that will have a couple of cells for miscillaneous spend. The information in these cells has to start z.1 Furniture, z.2 Racking etc.

I would like to allow people to specify what the item is by typing in the cell e.g. if i had a budget for cuddly toys i would want them to type into the cell Z.3 Cuddly Toy

What im trying to get round to saying is that is there a way that i can use data validation on a specific cell so that any information typed in that celll has z.x at the start.

Many thanks,

Chemist

Maybe try custom formula:

=AND(LEFT(A1,2)="Z.",ISNUMBER(MID(A1,3,2)+0),OR(MID(A1,4,1)=" ",MID(A1,5,1)=" "))

This checks first 2 chars are Z., checks that the next 2 characters (incl. space, if single digit number) is a number when coerced to a number, and checks that there is a space before the typed word.

If you could use two columns

Try
DataValidation In Column A > List > Source

Furniture,Racking,SomethingElse

In Column B

="Z."&ROW()&"."&A1

Fill/Drag Down to suit

Demo workbook attached

Hope this helps