Going through every instance of a string in text boxes

[h2whoa]

Sub Beta2()
   Dim oshp As Shape, osld As Slide, TxtChng As String, i As Integer
   
   
      For Each osld In ActivePresentation.Slides
      For Each oshp In osld.Shapes
         If oshp.HasTextFrame Then
            If oshp.TextFrame.HasText Then
                TxtChng = InStr(oshp.TextFrame.TextRange.Characters.Text, ChrW(&H3B2) & "2")
                
                If TxtChng > 0 Then
                    For i = 1 To 3
                        With oshp.TextFrame.TextRange.Characters(foundAt + 1)
                            .Font.Subscript = True
                        End With
                   Next i
                End If
            End If
         End If
      Next oshp
   Next osld


End Sub

Before I expand this code to have the option to have a user defined search term (rather than being fixed to β2, as it is now), I've realised that something is still not quite right with this. I think I know, broadly, what is going wrong, but I don't know how to set it right.

The code as it currently stands will only change β2 to β₂ for the first instance in each text box. If there is more than one β2 in the text box, it will only do the first one. I tried adding the i loop, thinking this would make it run through the whole text box, but I realise now that this was stupid, and that it's just applying the change to the first β2 three times!

Is there a way to get this to change ALL of the β2 in each text box to β₂?

My grand plan is to expand this code to be a functioning search and replace for text that needs superscripts and subscripts (hence my previous question about versatile inputboxes), but I want to get this bit right before trying out anything more extensive.

Thanks for your help!