Calcuate difference in one column based on value change in another column

Hi all,

Please see the attached screenshot. I want to calculate
the difference in column U cells when the column V value
changes from 1 to 0 and back again.

So in this example, W26 should show the difference
between U26 and U4 since rows 26 and 4 are the
rows where the V value changed from 1 to 0 and
from 0 to 1, respectively.

Thanks for your help!
Mark