How do I not allow duplicates in a drop down

How do I make it so no duplicate show in a dynamic drop down. Pulling from ACCESS.

Form Code:

<form name="frmSelect" method="get" action="dbsearch.asp">
<!-- Using javascript with ASP for an automatic submit of selected form value***jmeyers -->
<SELECT name=DbName LANGUAGE=javascript onchange="return dept_onchange(frmSelect)" title="Select exercise to display cooresponding observations." style="color: #003366; font-style: normal; font-family: verdana; font-weight: normal; font-size:10px">
<% ' Populating drop down menu from DbName field in Tbl_Observation table***jmeyers
do until drs.EOF
response.write("<option")
if drs.fields("DbName")=DbName then
response.write("selected")
end if response.write(">")
response.write(drs.fields("DbName"))
drs.MoveNext
loop
drs.Close set drs=Nothing
%>
</SELECT>
<font size="1"><font face="Arial, Helvetica, sans-serif" title="Select exercise to display cooresponding observations.">Select exercise</font></font>
</form>

Form action:

<% If oField <> "" Then
Set conn = Server.CreateObject("ADODB.Connection") conn.Open("DRIVER={Microsoft Access Driver (*.mdb)};DBQ=" & Server.MapPath("AssDB/EFCATDB.mdb"))
set rs = Server.CreateObject("ADODB.Recordset") sql ="SELECT DISTINCT ROW * " _ & "FROM Tbl_Observation WHERE [Tbl_Observation].[DbName] = '" & oField & "'" Set rs = conn.Execute(sql) %>

i'd reformulate your select query to get rid of duplicates.

Use a separate query for building the dropdown list and bundle it in a function or something. Then you can just SELECT DISTINCT [fieldname] FROM Table.