Linked drop-down lists

Lets say I have the following two named ranges:

Work Code........Work Description
1.....................Work1
2.....................Work2
3.....................Work3
4.....................Work4
5.....................Work5

Now on another worksheet in the same workbook, I make two drop-down lists (using data validation), one for each named range.

At the moment, I have it so when you change a row in the work code column, the same row in the work description column gets updated according ot the named ranges above. Eg. I choose 1 in the work code column, the same row in the work description column changes to 'Work 1'. To do this, I'm using the following formula for cells in the work description:

=IF($B6="","",LOOKUP($B6,workCode,workDescription))

Where $B6 is the address of the work code cell

I'm trying to make it so that the opposite operation will work as well... that is, if I change a row in the work description column, the same row in the work code column will get updated....

any help would be appreciated,

Thanks