Um.
Had you noticed that your two tests are identical?
So your code basically amounts to:
if updown1.Value > 1000
increase updown2.Value
else
decrease updown2.Value
So every time you change the value of the first updown and it's below 1000 you will reduce updown2.
It's possible that you want to reference updown2 in the second test - but I'm not sure what this code is meant to do.
And I suspect that you don't want increment or decrement at all - what if I paste the value 20000 into the first updown? Shouldn't the second change by more than one?