Decision table - working in both directions

Hi,

What is the common practice to make  decision table work in both directions ?

Example:

two columens: old number, new number

11111     AAAAAA

2222      BBBBBB

What would be the smart way to use this decision table in both directions (using old number or using a new number as a search criteria) ?

I know I can copy the table and create a new one but is this the only way ?

Thank you for any tips

Michal Krawczyk