SETRANGE function on the page

Hi, guys, I have a problem with SETRANGE function usage on a page. I have added CurrentJobNo variable to Job Card page. It should work this way: when I choose a different CurrentJobNo(validate this field), Job Card page should be filtered to only show those Jobs that have Job No. equal to CurrentJobNo.

So the code looks like this:

CurrentJobNo - OnValidate()

SETRANGE("Job No.",CurrentJobNo);
MESSAGE(CurrentJobNo);
MESSAGE("Job No.");

I do not understand why it doesn't work. As you can see I have two messages for testing. So the first message shows the correct value(example J0005) that I want to filter on, but the second message shows the old value. Why does SETRANGE do not filter Job No. to this new value??