Get number from a variable name

Hi everyone ! I've some difficult to find an answer to my problem..

Can someone explain me how to get a number from a variable and use in as an index with the "i" in a loop for ?

 //Coordoninates for the player 1
 x1 = P1.transform.position.x;
 z1 = P1.transform.position.z;
 function GetPosition()
 {
     //Check position form all players
     for(var i : int = 0; i<nCaseArray; i++)
     {
         xTotal = xTotal + (x+"i");
         zTotal = zTotal + (z+"i");
     }
 }

Then i search the syntaxe for call the " 1 " in x1 with the i ( index ) of my for loop !

Thanks a lot !