Please suggest reg express for every nth occurrence of a character in a string in vba - vba

Question

At the very outset, let me confess. I am not a developer nor do I have any technical background. However, I have learned a bit of coding. I want to a regular expression for finding every nth position of a character. For example, google, yahoo, rediff, facebook, cnn, pinterest, gmail. I want to find every third occurrence of the comma in the string and replace it with a semicolon. This is for a excel vba macro I am working on. For now, I am trying to loop through it and then replace. If the data is large, the macro fails. Would appreciate your reply. Thanks a ton in advance.
Here is what I am doing:
Option Explicit
Sub reg()
Dim regx As RegExp
Set regx = New RegExp
Dim allMatches As Object
Dim contents As String
Dim contents2 As String
contents = "hello, wow, true, false, why, try, cry, haha"
contents = "contents1" & contents
regx.pattern = ",{4}"
regx.Global = True
regx.IgnoreCase = False
Set allMatches = regx.Execute(contents)
contents2 = regx.Replace(contents, ";")
MsgBox contents2
End Sub
I get the data from all selected cells. Join it. Add semicolon (an indicator for the row end) at every fourth comma found. Please suggest if there is a better way to do it as I am new to this:
Here is what I have done currently by looping through array. I want to avoid this.
Function insertColon(sInputString As String) As Variant
Dim data3 As String
Dim sFind As String
Dim sReplacewith As String
Dim result As String
'Dim i As Integer
Dim Counter As Integer
sFind = ","
sReplacewith = ";"
data3 = sInputString
' MsgBox = data3
' Dim J As Integer
Application.Volatile
FindN = 0
'Dim i As Integer
' i = 1
Counter = 4
' MsgBox Len(data3)
While InStr(Counter, sInputString, sFind)
FindN = InStr(Counter, sInputString, sFind)
data3 = Application.Substitute(data3, sFind, sReplacewith, Counter)
Counter = Counter + 3
' MsgBox "loop" & i
'
' i = i + 1
Wend

Answer 1

If I understood you properly then all your code could be summarized to a few lines
Dim sText As String
sText = "hello, wow, true, false, why, try, cry, haha, huh, muh"
For p = 3 To Len(sText) Step 2
sText = WorksheetFunction.Substitute(sText, ",", ";", p)
Next p
MsgBox sText
'Output
'hello, wow, true; false, why, try; cry, haha, huh; muh
Test it and let me know whether it fails. If not don't forget to accept the answer.