VB判断字符串中是否有二联号

Visual Basic判断字符串中是否有二联号，三连号，比如13462220367，就是三联号

 dim n = 0
for i = 2 to len(s)
if mid(s,i,1)=mid(s,i-1,1) then n = n + 1 else n = 1
if n =3 then msgbox "三联":exit for
next