sorry I read the question incorrectly I thought you wanted the dispaly to vary from 0 - 25 over the entire range of 2.72 thru 4.52V

however it would appear from your question that all you have to do is multiply the difference between the actual value (2.98V) and the Lowest Value (2.72V) by 100

for instance your example
(2.98 - 2.72) * 100 = 26

fullscale
(4.52 - 2.72) * 100 = 180


THen again I may still be way of course


Marshall