Replace the SCAN/ENDSCAN with another DO WHILE

SELECT WorkListXMLCursor
GO TOP
DO WHILE !EOF()
      GroupHeading = GroupHeading
      DO WHILE GroupHeading = m.GroupHeading
            SKIP
            REPLACE GroupHeading WITH ""
      ENDDO
      SKIP
ENDDO

>I'm trying to only keep the first unique value of the GroupHeading field, blanking all others like it until I get to a different value. The code below is kicking out of the DO WHILE because the value of GroupHeading is changed by the REPLACE. I understand why, but how can I get around it?.
>

>			SELECT WorkListXMLCursor
>			SCAN
>				m.GroupHeading = GroupHeading
>				DO WHILE GroupHeading = m.GroupHeading
>					SKIP
>					REPLACE GroupHeading WITH ''
>				ENDDO
>			ENDSCAN
>