SelectCommand Issue with ASP.Net

I have a SelectCommand with Distinct in it but it continues to pull all records within a record set but I only want the first record of the record set displayed on the screen.  Each record set can have up to 50 records with a unique id, but the same sub number (aaid) in the record set.  The sub number relates to a header table.

Example (ID = Unique, AAID = SubNumber)
ID AAID
1  10
2  10
3  10
4  10
5  11
6  11
7  11
8  12
9  12
and so.

So within my aspx page I have the following SelectCommand:
SelectCommand="SELECT DISTINCT [AAID], [ID], [DOCLOAD_SEC1], [TRANS_CODE], [HEADER_DESCRIPTION], [LINE_NO], [TRANS_TYPE], [BEG_BFY], [ORGN], [OBJ_REV_SRCE], [JOB_NUMBER], [FUND], [PGMT], [VENDOR_ID], [LINE_AMOUNT], [EMAIL_ADDRESS_OF_SUBMITTER], [DATE_SUBMITTED] FROM [AA_DETAIL] WHERE ([DOCLOAD_SEC1] = @DOCLOAD_SEC1) AND ([LAST_MODIFY_USER] IS NULL) ORDER BY [AAID]">

Thanks for the assist.