Totalizer or PI Calc Help

I need to build a Totalizer or PI Calc that will perform the same function as this DataLink equation:

=PIAdvCalcVal("pi_tag","-7d","*","total","event-weighted",0,1,0,"pi_server")

I don't think a PI Calc will work since it cannot be event-weighted.

In short what I need is when a new value for "pi_tag" comes in the calculation returns the total of "pi_tag" for the past 7 days.  "pi_tag" can get anywhere from zero to two values per day.