Public Sub ChangeStyle( _
  ByRef strParam As String)
    Dim rng As Range
    Dim intFound As Integer
    Dim lngStart As Long
    Dim lngEnd As Long
    
    Set rng = ActiveDocument.Content
        
    With rng.Find
        .ClearFormatting
        
        Do While .Execute( _
          FindText:=strParam, _
          Forward:=True, _
          Format:=True) = True And intFound <  2 
          
            If intFound >  0  Then
                lngEnd = rng.Start -  1 
                rng.SetRange lngStart, lngEnd
                rng.Style = wdStyleHeading1
            Else
                lngStart = rng.End +  1 
            End If
            
            intFound = intFound +  1 
        Loop
    End With
End Sub