Leonid,
Thank you for posting this solution.
I'm comparing between "Confidence Intervals" (CI) from survey estimates.
I removed the "+1" to get the correct answer.
I also calculated the range as a proportion of the widest CI as follows:

overlap=(MIN(ucl_a,ucl_b)-MAX(lcl_a,lcl_b))/(MAX(RANGE(lcl_a,ucl_a),RANGE(lcl_b,ucl_b)));