Program search

I maintain a few Signs in our little community.
The information on these signs is changed frequently.

I need a program that will list all the letters used on the sign in
alphabetical order and how many of each letters are used.

Example:

Have a Great Day

A = 3
D = 1
E = 2
H = 1
T = 1
V = 1
Y = 1

This would allow me to know if I have a sufficient supply of letters
to complete the signs or , if I need to make changes if I don’t have enough of
any letter.

Thanks