DATECONV from transformation library.

I'm trying to use the DATECONV function identified in the transformtion library in a transfer rule routine. I cannot seem to resolve the syntax required. I'm getting the following error message:

E:Comma without preceding colon (after ZRESULT ?).

My code is as follows:

RESULT = DATECONV( ZOPTDTE, 'MDY', '/' ).

We are on support pack SAPKW31019.

Thanks for your time.