replace all characters in only a portion of a line

Let's say I have a file of lines and some of the lines are of the form:


Name: <a first name> <possibly attributions like M.D.>


Such as:


Name: Bart Simpson, MD


and I want to redact the name part only with a 1:1 substitution of
letters to asterisks so that the result is:


Name: **** *******, MD


So effectively I want to do a 's/[A-Za-z]/*/g' only on the portion of the line that comes after the ": " and before any ,.


Is there any way to do this with sed?


Cheers,
b.




[Non-text portions of this message have been removed]