In excel I have 
- Column A with unique IDs
- Column B with text data
I need a script or formula to query A where the Unique IDs match and
then to join Column B data together seperated by a semicolon

Hello!
In order to accomplish that, try following these steps:

1) Sort your data by ID using the sort button. The order (ascending or
descending) doesn't matter.

2) We'll put the joined text in column C. In cell C2 (or whatever row
in which you have the first piece of data) enter the formula:
=B2

3) In the next row (cell C3 in my example) enter the formula:
=IF(A3=A2, C2 & ";" & B3, B3)

4) Drag the formula in step 3 to your last row.

That's it! I've made an example file for you so the idea is clear. You
may download it from:

http://www.filefactory.com/dlf/f/b0f278/

Notice that it's important to sort your data by ID before applying the formulas.


I hope this helps! If you have any doubt regarding my answer, please
don't hesitate to request clarification before rating it. Otherwise, I
await your rating and final comments.

Best wishes!
elmarto