Sheet linking and sum of same cell in different sheets

Hello,

I am trying to achieve 3 things - I am quite competent in excel yet I am have never attempted to do this before. Anyway, onto the problem(s):

I have a large amount of worksheets and have created an index page to easily select the worksheet I require. However, since I have never done this before, I am not sure how to

1) Link to the worksheet I want
2) Keep the index page displayed in the bottom left so that it is irrelevant which sheet is currently selected - I can easily click on index and switch to another sheet if needed
3) I have a total on each page, and am going to have a grand total displayed on the index page. The total on each page is in cell D1, is there some formula I can use rather than having to put in =SUM(Sheet1!D1+Sheet2 !D1+Sheet3!D1+Sheet4!D1 ... etc)

Thanks for any help!
Tim

=SUM('Sheet1:Sheet4'!D1)



Hope it helps!