Checking for NULL in RTF

Hi,

I am using Document Management (similar to WebADI) to generate letters out of Oracle EBS.

The rtf template that  is used for the letters is created similar to the XML RTF templates. All notes in MOS realted to document management template creation guide to the XML Publisher Guide.

I used the guide for creating the template and I am able to carry out all the simple tasks - such as populating the placeholder tags with data and carrying out conditional checks using <?if:   ?> <?end if?>.

I need the template to check for NULL. I tried the example given in the guide but it is not working for me.