Thats what I hoped, cool, thanks for that. So any #var assigments would also have to be locked for the entire required duration of the existance of that var or it will be overwritten by a different browser instance assigning a different value to that same named #var? Ok just to 100% sure..... What would happen if the value of 1 was assigned to #counter in browser 1, then 5 seconds later the value of 2 was assigned to #counter in browser 2 (assuming the assign code wasnt in a lock) then 3 seconds after that, the code in browser 1 added the value of #counter to a global list? (add to list