[TYPO3-english] making one of the two fields compulsory in powermail

[Rupali]

Hallo list,

in our contact form, we want to make telephone no. or E-mail address to be
mandatory field, but not both. In powermail manual i got these codes for it:
[globalVar = GP:tx_powermail_pi1|uid6=  ]
[else]
plugin.tx_powermail_pi1.validate.uid7.required = 1
[end]
but unfortunately its not working. uid6 (tel no) and uid 7 (e-mail) are not
atall taken to be mandatory.
can anybody tell how to do this?

Thanks and Regards,
Rupali