Pi Datalink and Excel

Hi

I am working on Excel with PI. Now I have different cells which calculate average from the dates I manually enter in my calculation something like that.

=PIAdvCalcVal(Tags!$B$17,"10  JUL 2013 00:00","11 JUL 2013 00:00","total","time-weighted",0,1,0,"server")

1. Now I want that each day, it should calculate the same but I dont have to manually enter the date of each day so when I open Excel it has the value corresponding to that day? Can you tell me how it can be done?

2. Now, as a next phase to question 1, I want to make sure that a copy of earlier sheet is created for each day, and that values are assigned correspondingly in that sheet. And for next day it goes?
Or maybe anyother approach will be appreciated

3. And also If I want to access PI tag values in Excel VBA, what necessary initialization should I do on top of VBA code.