Auto fill matchingl text / number vice versa

Hi all,

I want to create a word doc would auto fill matching base on what I type whether it be a number or a text.
Sort of like a string~ let me explain clearly in a example:

If I type the word one the following designated area will auto fill the number 1.

If I type the number 1 the following designated area will auto fill the word one.

vice versa

I need to "string" this in word 07 because I am creating a document for clients to fill out and it's to ease the redundancy of them or me typing the number and then the word to that number multiple times.

Thanks in advance.