I've established why the modify_date column was changing although I've not tracked down precisely *what* was making the change. It was both obvious when I thought about it and...

No need to apologise Pietlinden, especially when you've just taught me something too.  I didn't realise running totals had become so straightforward.

However.... The OP's after a solution that...

If there is no way to establish the order of the rows this can't be done properly.  If you don't know what value is first then second and so on...

Ok, that's better but it's still not hugely clear.

Are you adding all three tables together for all ID's?  You appear to have used ID 1 for all your...

There's not a lot to go on there. There's a huge number of reasons why your report isn't returning anything.  You'll need to provide much more detail to get a...