remaining workload changes

I guess you don't want an alerts on remaining workload changes, but on revised workload changes.

Left work (remaining workload) changes every time someone enters real work, so this is very (yes very very) often.
So I think you are interesting on reevaluation of left work that changes the total work (real + left = revised)

There is no alert on all changes.
All you have is an indicator on revised compared to assigned (or compared to validated)
If you use revised compared to assigned and set alert at 110%, you'll get a message when revised = 110% of assigned.
So if you set the indicator at 101%, you'll get an alert when resised is over assigned (of 1%).
But you'll get the alert only once, not on all changes.
You can just set to values : warning (for instance at 1% to highlight any increase) and alert (for instance à 20% when over use becomes unbearable.