Update Error

[enrmpaga]

i'm trying to update the record 'AmountInStock' but i'm getting this error:

Microsoft OLE DB Provider for ODBC Drivers (0x80040E10)
[Microsoft][ODBC Microsoft Access Driver] Too few parameters. Expected 1.

CODE:

Set RS = Server.CreateObject("ADODB.Recordset")
Set objConn = Server.CreateObject("ADODB.Connection")
objConn.ConnectionString = "DSN=pagans"
objConn.Open

IDKEY=CStr(Request.querystring("IDKEY"))

sql="UPDATE acc SET AmountInStock = "'&AmountInStock&'" WHERE IDKEY = "'&IDKEY&'" "
sql=sql & "AmountInStock = AmountInStock -1 "
objConn.Execute sql