I'm new in Excel having recently moved from another spreadsheet brand that
didn't require the "=" preceding a formula so I'm constantly running into the
problem of having to go back and insert the "=" in each formula cell. To do
this, I came up with:

Sub Equation()

With Selection
.FormulaR1C1 = "=" & .FormulaR1C1
End With

End Sub

.... which works perfectly as long as only one cell is selected. If I select
a range of cells I get the error message:

Run-time error '13':
Type mismatch

What to do?