identity of the logged in user

I want to be able to embed a filter that uses  identity in the select list of the query parameter on a BI Custom report in unifier.

There are multiple users that have access to the report but the value they should be able to select in the query parameter should be restricted based on the requesting user.

Example.

Vendor  PO Number

ABC      1234

ABC      1235

BCD      4321

CDE      5321

Then when the user associated with Vendor ABC executes the report only the PO's 1234 and 1235 should show up in the query parameter select list.

Don't want to create multiple reports and/or do filtering in the BI template.