[Zope] Problems with External Script

[Ben Ocean]

Hi;
I have this external script:

import string, os

def myaffiliateprogram():
  user_id, banner_id, page =3D=20
context.REQUEST['user_id'],context.REQUEST['banner_id'],context.REQUEST['pag=
e']
  redirect =3D=20
"http://www.myaffiliateprogram.com/u/%(user_id)s/t.asp?id=3D%(banner_id)s&p=
=3D%(page)s"=20
% locals()
  print "Location: %(redirect)s\n" % locals()

When I call the script in a DTML Document it throws this error:

Site Error
An error was encountered while publishing this resource.
Error Type: NameError
Error Value: global name 'context' is not defined

Troubleshooting Suggestions
=B7       This resource may be trying to reference a nonexistent object or=
=20
variable global name 'context' is not defined.
=B7       The URL may be incorrect.
=B7       The parameters passed to this resource may be incorrect.
=B7       A resource that this resource relies on may be encountering an=
 error.
For more detailed information about the error, please refer to the HTML=20
source for this page.
If the error persists please contact the site maintainer. Thank you for=20
your patience.

What am I doing wrong?
TIA,
BenO