Use asFewOfPattern to match as few individual letters as possible between two instances of "b".

Create txt as a string. Create a pattern, pat, that matches as few of the letters "a" or "b" as possible between two instances of the character "b".

txt = "bb bab babab babaaabab";
pat = "b" + asFewOfPattern("a"|"b") + "b";

Use replace to replace text matched by pat with the character "*".

replace(txt,pat,"*")

ans = 
"* * *ab *aaa*"

Use asFewOfPattern to match as few individual letters as possible between two instances of "b" but require at least three letters.

Create txt as a string. Create a pattern, pat, that matches as few of the letters "a" or "b" possible between two instances of the character "b", but specify that there must be a minimum of three matched letters.

txt = "bb bab babab babaaabab";
pat = "b" + asFewOfPattern("a"|"b",3) + "b";

Use replace to replace text matched by pat with the character "*".

replace(txt,pat,"*")

ans = 
"bb bab * *ab"

Use asFewOfPattern to match as few individual letters as possible between two instances of "b", but require at least three and no more than four letters.

Create txt as a string. Create a pattern, pat, that will match as few of the letters "a" or "b" as possible between two instances of the character "b", but specify that there must be a minimum of three and no more than four letters.

txt = "bb bab babab babaaabab";
pat = "b" + asFewOfPattern("a"|"b",3,4) + "b";

Use replace to replace text matched by pat with the character "*".

replace(txt,pat,"*")

ans = 
"bb bab * ba*ab"