How to have the H and L of the shortest range of th days ?

I'm trying to create an indicator that:

1. User defines number of periods

2. Indicator looks back and finds the lowest range (H-L) of those bars

3. Indicator plots today the H and L of that bar


What's the easiest way of doing it ?
Do I have to use a loop with "for - to" until I find the lowest range bar and then define 2 variables with H and L of that bar ?