Change The Colour Of A TextBox / Field Depending On It's Value?

Hello fellow programmers,

I have a tricky one for you. We have decided to split our local City up into different zones. Giving each zone a number and assigning it a colour.

I have a form with all the customers who want jobs done in different parts of the city. This form has a text box on it called: Zone - (which has a 3 digit number it it).

I want the colour of the text box to change depending on the Zone number, in the continuous Form view.

So all the customers living in Zone=111, will have a Red background colour (color), all living in Zone=222 will have a Green background colour.

I know conditional formatting through the properties of the Form can be used, but it only allows me to select 3 different situations. I have many more than 3 colours that I want to assign.

I am working on a VB module to define what colour numbers from the MS Access Colour Map will be assigned to each Zone number.

How can I now apply this module to the form, so when it opens, all the customers who live in Zone=111 will have a Red coloured background, those living in Zone=222 will have a green colour background, etc?