Letter refer to number

I did use A B C D E F ... for 1 2 3 4 5 6 .... with the following code:

Nr=[1 2 3 4 5 6];
Letter=char(Nr+'A'-1);
Letter =
ABCDEF

But now i want to get back the originals number instead of the corresponding letters (Nr is not avaible anymore).

Answer 1

[C.J. Harris]

Nr2 = double(Letter)-'A'+1