Numbering by Letters

[abc]

I can number my rows by using position() to display:
1.
2.
3.

How do I number them as letters? to display:
A.
B.
C.

 

[bratt]

can you try something like:
substring("ABCEDEFGHIJKLMNOPQRSTUVWXYZ", position(),1)

 

[abc]

THANKS! it works!