Update query using a string in the criteria

Hi there,

I'm sure this is an easy one to resolve but i can not for the life of me figure it out.

DoCmd****nSQL "UPDATE PSA SET PSA.Ref_ID = (NewRef_ID) WHERE (((PSA.Ref_ID) = 'Temp'))"

NewRef_ID is a string which contains a value which i want to use, so field Ref_ID gets updated with the value held in NewRef_ID.

When i run the query i get a pop up box asking me to enter the value for NewRef_ID. :mad:

thanks
Marcus