syntax fejl

Hej

Jeg for at vide at der er en syntax fejl, når jeg prøver at køre dette:

IF productID <> "" THEN
  sqlString = "SELECT cart_id FROM cart " &_
    "WHERE cart_userID=" & userID & " " &_
    "AND cart_productID=" & productID
  SET RS = Conn.Execute( sqlString )
 
  productname     = Request.Form("product_name")
  productvhsdvd = Request.Form("product_vhsdvd")
 
  IF RS.EOF THEN
  sqlString = "INSERT INTO cart ( " &_
    "cart_productname, " &_
    "cart_productvhsdvd, " &_
    "cart_userID, " &_
    "cart_productID, " &_
    "cart_quantity " &_
    ") VALUES ( " &_
    productname & ", " &_
    productvhsdvd & ", " &_
    userID & ", " &_
    productID & ", 1 )"
  ELSE
  sqlString = "UPDATE cart SET " &_
    "cart_quantity=cart_quantity+1 " &_
    "WHERE cart_id=" & RS( "cart_id" )
  END IF
  RS.Close
  SET RS = Nothing
  Conn.Execute sqlString
END IF

Er der nogen som kan fortælle mig hvor ??