SKILL function question

I am a beginner at best in SKILL, but I am trying to modify an existing routine.  Here is the part of routine I am working on.  Previously, I filled in a Radius in a form, but I would like to modify the routine so that Radius is 20% of Height, with a maximum Radius of 0.25 and a minimum of 0.01.  The text in bold is what I started, but like I said, I don't really know what I am doing.  I am sure this is an easy fix.  Can one of you experts show me the correxct way to handle this please.

(defun _ns_spad_outform_run ()
    let((Length Height Radius ls1 ls2 ls3 ls4 ls5 ls6 ls7 ls8 ls9 pad_path)

        Length   = axlFormGetField( _ns_spad_outform "boxx")
        Height   = axlFormGetField( _ns_spad_outform "boxy")
;        Radius  = axlFormGetField( _ns_spad_outform "radius")
    (  if ( (Height > 1.25) then Radius = .25
      else
    Radius = Height*.2)
     )

Thanks.

Chad