Sub ExampleWriteExpression()
    'insertion point should be in equation. Metric expression written (wdOMathFunctionScrSub) at end. Then
    Dim LetterCode As Integer, Letter0 As Integer
    Dim Equation As OMath
    Dim MathTerm As OMathFunction
    Dim MyRange As Range
    
    If Selection.OMaths.Count <> 1 Then ExpanderFatalError ("Cursor must be in an equation.")
    Set Equation = Selection.OMaths(1)
    Set MyRange = Equation.Range
    MyRange.Collapse (wdCollapseEnd)
    Set MathTerm = Equation.Functions.Add(MyRange, wdOMathFunctionScrSub)
    MathTerm.ScrSub.E.Range = "g"
    MathTerm.ScrSub.Sub.Range = ChrW(&H3BC) & ChrW(&H3BD)
    Set MathTerm = Equation.Functions.Add(MyRange, wdOMathFunctionNormalText) 'does not add anything to Equation.Functions
    Set MathTerm = Equation.Functions.Add(MyRange, wdOMathFunctionText) 'error 6219
                                                                        'The text function cannot be applied to a selection
    'We do want to add a wdOMathFunctionText, because that is the kind of function we had 
    'when the original equation just contains X or X= as can be seen in the debugger
End Sub