populating a datacombo based on the results of another

i am trying to populate a datacombo box based on what has been chosen from another using the following code:

Dim RS As ADODB.Recordset
Set RS = New ADODB.Recordset

Dim strProductType As String
strProductType = DataComboType.Text
Dim descSQL As String
descSQL = "SELECT Product.Description FROM ProductType INNER JOIN Product ON ProductType.TypeCode = Product.TypeCode WHERE ProductType.Description= '" & strProductType & "'"
Set RS = Conn.Execute(descSQL)
RS.MoveFirst
Do While Not RS.EOF
DataComboProduct.RecordSource = descSQL
DataComboProduct.ListField = RS.Fields(0)
RS.MoveNext
Loop

However, the second combo box does not populate at all - why is this? Thank you!

Datacombo is not populated with a loop because it is a data bound control.

Set RS = Conn.Execute(descSQL)
Set DataComboProduct.RowSource = RS
DataComboProduct.ListField = RS.Fields(0)
'in order to make the first item appear in the box
DataComboProduct.DataField = RS.Fields(0)