Need to extract data based on userid - Confuse on term to "aggregate"

Need to extract data based on userid - Confuse on term to "aggregate"

Hello,

I have a report that have many dates for many customer. I want to extract the list of all dates that pertains to a specific customer, logged  in the portal, and then find the next upcomming date.

Is that what is call aggregate ? Or fetch ? (english is not my first language...).

Right now I am abble to find the next date with this script, but not attached to the loginuser:

ProchaineLivraison = Calendrier_maitre[Date_Livraison > zoho.currentdate].minimum(Date_Livraison);
alert "Votre prochaine livraison sera le " + ProchaineLivraison;

Can somebody help me with this, and tell me the name of the function !

Also, is the workflow can be trigger with "portal access" ?

Sylvain