Generate 7 random numbers and 2 random letters

I have some code to generate 5 random numbers for a customer ID.  My client would not like it to be 7 numbers ( I can handle that), but they also want two letters to appear anywhere in the string, for a total of 9 characters (7 numbers, 2 letters).  Again, the letters can appear anywhere, random, beginning, end, together, etc.

Does anyone have a function already built for this or have some q & d code?

Thanks!

-Scott