Tag Value Via VBA

First at all, sorry my english.

I know that if i want to get a tag value, i can create a Value, insert its tag and use the command: tagValue = getValue(vrDate, vrStatus).

Is there a way to get a tag value using no Value Box via VBA? Direct from the server?

Some thing kind of: tagValue = piValue("tag","starttime", "endtime","server")

My problem is:

I got a display with 20 value boxes. Each of this value box returns me a following expression: "TAGAVG('tag', 'starttime', 'endtime').

But it is getting too much time to calculate, because my: endtime - starttime = 1 year. So, i want to try to get the tag value without these value boxes

I hope i have understood my question. Thanks!