Variable Drop Down Lists

Hi

1st post but i've found invaluable help in the past from this site, but really stuck on something now.

I've created a variable drop down list for 4 different categories all linked, but I can only get it to link on the first line - the plan could have any number of actions which need to go in these categories (i've put 50 down as an example).

Is there a quick way or will I have to do different data validation for each line of the action plan?

Cheers