[Zope] FW: [Zope] Newbie DTML: Checking a variable

I have the following code in my zope page and its just not working for me.

<td width=""><input name="ssn_call" width=30 value= <dtml-if "REQUEST.value('ssn_call', ' ')"> "" <dtml-else> "<dtml-var SSN>" </dtml-if> ></td>

I am trying to clear a Blank for the empty condition.

-Bryan