You can't do this. Sending personal data (like emails or phone numbers) to Google Analytics is against their Terms of service (Section 7):
You will not (and will not allow any third party to) use the Service
to track, collect or upload any data that personally identifies an
individual (such as a name, email address or billing information), or
other data which can be reasonably linked to such information by
Google.
Talking generally, if you really want to register only one data point of the two potentially available, it should be done server-side (the exact code depends obviously on what system and language are you using) and sent the result as a parameter to Google Analytics .
Alternatively, you could obviously register two data points at the same time (not just one or the other) using two parameters. You can put for example one as the "action" parameter and the other as the "label" parameter, like in this example
_gaq.push(['_trackEvent', 'Friday Deals', 'DATA1', 'DATA2']);
Or use the other optional parameter "value" to register a number. For example:
_gaq.push(['_trackEvent', 'Friday Deals', 'Music and Sports', 'DATA1', '54646465']);