Creating a lookup field that contains calculation?

![So I created a lookup table, how would go about truncating via a lookup?

For example,

Choices 56, 56SW, 56FR are using the same calculation

Choices DDS IDSL, ISDN TR, ISDN are using the same calculation

choices HDSL, HDSL2, HDSL4 are using the same calculation

What would be the best way to go about that....

Is there a way to have the user choose a one of those and then perform the calculation?

So if user chooses HDSL2 it will do the HDSL calculation, same thing if user chooses HDSL4 instead it will do the HDSL calculation since HDSL, HDSL2, AND HDSL4 are the same calculations...

Choices DDS IDSL, ISDN TR, ISDN are using the same calculation

choices HDSL, HDSL2, HDSL4 are using the same calculation So if user chooses HDSL2 it will do the HDSL calculation, same thing if user chooses HDSL4 instead it will do the HDSL calculation since HDSL, HDSL2, AND HDSL4 are the same calculations...

Any help would be appreciated ]1