Dynamic reference table from a table source

Hi all, hoping someone can help me;

I'm trying to write a formula to insert in "list" feature of the data validation block. I want to create a dynamic reference list from the standard table, so if the data in the source table is changed, the reference list can find the data associated with a particular value. A VLookup formula works great if there is a one to one relationship, the issue I'm wrestling with is in the table the lookup value needs to return a list of associated values.

I can't really change the structure of the reference table, because it is a standard export from salesforce.com

If anyone can help, please do!!!

I tried this, but it returns an error ... I can't figure out what the error is:

=INDIRECT(VLOOKUP(C20,'Insert Report Data here'!C:D,2,FALSE))