Notes/Domino 4 and 5 Forum

I am trying to write an agent that will append some text to the body field of a document. I have very little knowledge of Lotus Script so I am trying to do this through Formula Agent. I tried writing FIELD Body := Body + "----" + @now which gives an error "ERROR: Incorrect data type for operator or @Function"

Apologies if this is a very stupid question !!