Display content of cell if other cells are empty otherwise perform SUM

[peakoverload]

I'm only just beginning to get to grips with Excel and have hit a bit of a problem that I can't solve because I don't really understand what the formula I'm using actually does.

I have a range of cells, F14:F26, which track what page someone is up to in a book, so each time they read a book they enter the page they are up to in the next row of that range.

Another cell, F6 displays the total number of pages in that book.

I then have another cell, G5, which works out how many pages there are left to be read and for that I use this formula:

=SUM(F6-(INDEX(F14:F26,MATCH(9.99999999999999E+307,F14:F26))))

This works fine as long as something has been entered into one of the cells F14:F26 but if someone hasn't started to read that book then G6 displays #N/A because nothing has been entered in F14:F26.

What I would like is for G6 to display F6 if F14:F26 are empty but then to use the above formula IF something has been entered. The trouble is I got the above formula from another website and I don't fully understand exactly what it is doing which makes changing it to do what I need a bit tricky!

Anyone know how I can amend the formula to work how I need?

[zbor]

Try:

=IF(COUNT(F14:F26)=0, F6, SUM(F6-(INDEX(F14:F26,MATCH(9.99999999999999E+307,F14:F26)))))

[peakoverload]

Try:

=IF(COUNT(F14:F26)=0, F6, SUM(F6-(INDEX(F14:F26,MATCH(9.99999999999999E+307,F14:F26)))))

You are a STAR!!

I've been staring at that formula for ages waiting for the coffee to kick in but without success.

Thank you so much, you've saved me from getting any balder