Mandatory evaluation of suppliers

I would suggest you a workaround where the pm gets an email with the tasks where these field is not field. It's not an easy write down, but these are the steps:

1. You should create a filter (I think you can not filter the empty evaluation). It can be done with a custom field and a macro

2. Create a view which uses this filter

3. Create periodic jobs which will send the email to each pms with there tasks.

We did some kind of thing.

We just started something similar, but less automated. We generated a view to review jobs (by PM) that are not evaluated. That is used as part of our weekly check-ins with our PMs. 

We just implemented something very similar to Viktor's suggestion. It's a little simpler (no macros required), because it turns out we can filter out jobs where the evaluation is empty:

1. Create a View in the Jobs scope with the following filters (and any other filters you want to set):
   "Evaluation" ≤ 0 (that's a less-than or equal sign – crazy, but it works)
   "Project Manager" is "Signed-in User"
2. Make sure this View is shared with your PMs
3. Create a periodic job to run regularly and send this View to your PMs

Your PMs will get an email at the interval you specify which will contain a list of all their jobs that have not been evaluated yet. In the periodic job there's also a checkbox with the name "Don't send when report is empty" – check this box and your PMs will not get an email if the list is empty.

We have it set up to run once a week and only show jobs from the week before.

Nice! :-)