Operation not supported in this version using 8.5 designer

I am receiving the following error while running the agent as scheduled.“Operation not supported in this version”

I don’t have this error while running this script through web or from lotus notes client.

The following developed using 8.5.1 designer and running in 6.5.5 server

CODE

fldvalue=“TEST”

fldvalue=Replace(fldvalue,“”,“”)

Failing in Replace Function…

Any idea…please help