drop down without submit button

I am fairly new to ASP and have never used javascript with it ...
Here's my problem.
I have a form with 2 drop down boxes among other stuff. The second dropdown box will populate depending upon the value selected in the first drop down. I need a way to submit the value selected in the first drop down; just as soon as it is selected or when the user moves to the next tab. It should not have a submit button.
(Once a value in the second drop down is selected, and the user clicks update, the control passes to another page.)

I tried using the onChange() for the <select>

<% DIM dept %>

That's the js code .. I'm pretty sure it's wrong
<SCRIPT LANGUAGE = "JavaScript">
//To get the building from the dropdown and display the appropriate rooms

function whichDepartment(department)
{
dept = department
return department
}

</SCRIPT>

<%

That's the drop down.
<select name="Dept" onChange="return whichDepartment(this)">
<%
strSQL = "SELECT * FROM Department " &_
"ORDER BY DepartmentName "
objRstAdd2.open strSQL, objConn

WHILE NOT objRstAdd2.EOF
%>
<option value="<%=objRstAdd2("DepartmentID")%>"><%=Mid(objRstAdd2("DepartmentName"), 1, 10)%></option>
<%
objRstAdd2.MoveNext
WEND
objRstAdd2.Close
%>
</select>

And thats the second drop down, which uses dept from the first drop down

<select name = "room">
<%

'dept = request("Dept")
strSQL = "SELECT Room FROM Room " &_
"WHERE Room.BuildingID IN (SELECT BuildingID FROM Building WHERE BuildingName = '"&authorizedBuilding&"') AND "&_
"Room.DepartmentID IN (SELECT DepartmentID FROM Department WHERE DepartmentName = '"& Dept &"') "&_
"ORDER BY Room "
objRstAdd2.open strSQL, objConn

WHILE NOT objRstAdd2.EOF
%>
<option value="<%=objRstAdd2("Room")%>"><%=(objRstAdd2("Room"))%></option>
<% objRstAdd2.MoveNext
WEND
objRstAdd2.Close
%>
</select>

Help!

Please post you questions in the correct area of the forum. The code bank is for sample code only.

My apologies. Won't happen again.