Creating a relationship using a calculated column

[Anonymous]

Hi all, 

I am trying to connect 2 tables using the common column postcode. One column however is formated "#### ###" and the other table's column is formatted "#### #" so i created a calculated column in one table so it formatted in the shorter format. However, when I go to create the relationship between the 2 tables, the calculated column doesnt come up as one i can select. Does anyone know why this may be?

Thanks,

[amitchandak]

@Anonymous , The information you have provided is not making the problem clear to me. Can you please explain with an example.
Can you share sample data and sample output in table format?
Appreciate your Kudos.