assuming you are using the Adobe Analytics (SiteCatalyst) enterprise option to do your DPS analytics you can use the following custom events (varies a bit on SDK version I believe but enumerable from AnalyticsService.ALLOWED_EVENTS). "customEvent1", "customEvent2", "customEvent3", "customEvent4", "customEvent5", "customEvent6", "customEvent7", "customEvent8", "customEvent9", "customEvent10"
And they are pre-wired to these internal Sitecatalyst events. events 46-50 and 96-100.
More details here: http://download.macromedia.com/pub/developer/dps/analytics-report/dps-analytics-report-guide.pdf page 61.
Also, an event is a Metric, so this is some sort of number. So the second parameter(variables String Other variables to be assigned to the event) likely needs to follow the SiteCatalyst event constraints. They are of type "Counter" so you can either increment them by 1(no value) or an integer number. I have not tired this, but that is what I assume.