DTP Filter to exlclude Blank Materials

Hi, I have a Direct (no psa) Flat File Data Load via DTP into my InfoCube. Now I want to filter out any records with Blank Materials. When I go to set the filter in the DTP it seems it only allows me to INCLUDE selections and not EXCLUDE selections.

Any ideas how I can EXCLUDE Blank Materials from my Direct Flat File Load using the DTP? Or any other ideas?

Thanks!