Change Date format in a SmartForm

Hi,

I am trying to change the date format of the document date in an invoice smartform to MM.DD.YYYY.

However when adding

/: SET DATE MASK = 'DD.MMM.YYYY'. (this is what I used in regular forms)

I receive a error as if the statement is not recognized in SmartForms.

Can anyone tell me what is the correct statement for smartforms and where to add it ?

Thanks,

Mark