approval procedure

hi all

i am trying to create a approval procedure so that the purchase person cannot create a PO when the warehouse code is 09. this is the query i used

SELECT 'true' FROM OPOR T0 INNER JOIN POR1 T1 ON T0.DocEntry = T1.DocEntry WHERE $por1.WhsCode ='09'

it does not seem to work. i get an error saying could not commit transaction(adoc). is my query wrong?

could anyone help?

thanks!

prem