Bar Numbers With Letters

[Steph Phillips]

Hey All!

I'm looking for how to set some bar numbers in my score to have letters.
For example:
46, 47, 48, 48A, 48B, 48C, 49, etc...

I've been looking at the documentation and I see how to achieve this for 
\repeat'ed bars, but this is just sequential music and so the example in 
the documentation doesn't really apply here.

Thanks in advance!
~Steph