enter only even numbers in a combo box

[109bow]

I have a combo box where users can select from one of a number of even numbers, located in a table. The problem is users can also type a number into the box, they could by mistake enter an odd number, which would return incorrect data.
My question is, is it possible to add a clause somewhere in the combo box properties to restrict typed in numbers to even numbers only.

The row source of the combo box is;
SELECT [even units].[even number] FROM [even units] ORDER BY [even number];

Many thanks

 

[isladogs]

Set 'Limit to list = Yes' in the combo box properties window

 

[109bow]

Thanks ridders, so simple when you know!