Make a SELECT DISTINCT in Reporting Services

Hi,
I have a stored procedure, that can't be modified.
It return data like these (the real one is more, and more complex of
course)
A ...
A ...
A ...
B ...
B ...
B ...
C ...
C ...
I want to make a table with only theses entries :
A
B
C
How can i do it in reporting services ? I have tested
=Distinct(Fields!Qu_HA_LIB.Value, "GESCCNS")
But Distrinct seems to be not recognized by RS 2000
Thank you in advance
MassanuCan somebody help me, please ...