How to find and replace with macro in powerpoint without affecting the formatting?

The code below can find and replace text within a powerpoint file, however it clears individual formatting of words within the text boxes. That is after running this code all part inside the text box will be formatted like the first character. I would like to find and replace without affecting the formating.

As an example the power point would have a textbox with the following text:

Introduction
text used for testing the macro[1] and has different formatting

This is the result when I run the code

Introduction
text used for testing the macro[2] and has different formatting

This is the expected, ideal result

Introduction
text used for testing the macro[2] and has different formatting

 Sub DataScrubAllSlidesAndTables()
    Dim OldTxt As String
    Dim NewTxt As String
    OldTxt = "[1]"
    NewTxt = "[2]"
    
 
 
    Dim sld As Slide
    Dim grpItem As Shape
    Dim shp As Shape
    Dim i As Integer
    Dim j As Integer
    Dim varTemp As Variant
    For Each sld In ActivePresentation.Slides
    For Each shp In sld.Shapes

        If shp.HasTextFrame Then
            If shp.TextFrame.HasText Then
                shp.TextFrame.TextRange.Text = Replace(shp.TextFrame.TextRange.Text, OldTxt, NewTxt)
            End If
        End If

    

    Next shp
Next
End Sub

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