Public Sub AddProcToWs()
    Dim wb As Workbook
    Dim cm As CodeModule
    Dim lngI As Long
    
    Set wb = ThisWorkbook
    Set cm = wb.VBProject.VBComponents("Лист1").CodeModule
    
    With cm
        lngI = .CountOfLines +  1 
        .InsertLines lngI, "Private Sub Worksheet_SelectionChange(ByVal Target As Range)"
        lngI = lngI +  1 
        .InsertLines lngI, "MsgBox ""Hello!"""
        lngI = lngI +  1 
        .InsertLines lngI, "End Sub"
    End With
    
    Set cm = Nothing
    Set wb = Nothing
End Sub