Operator Overloading in Excel VBA

Not possible in VBA. VBA was intended to provide scripts which help with automation. You see, we call them macro. VBA is not built on top of modular classes or objects. Your VBE writes direct P-code the moment you type/ hit enter in the editor. VBA is awesome and packs alot of features but expecting these kind of facilities in VBA is a bit of stretch. No possibility to have this feature even in future. and Just a suggestion, never worry too much about code-cosmetics, they are useless overhead.

Here is a hack using the Worksheet_Change event. You can essentially place in a cell that contains a "+" character anything you want, thereby effectively disengaging the "+" signs normal function.

Private Sub Worksheet_Change(ByVal Target As Range)
If UBound(Split(CStr(Target), "+")) > 0 Then
    Target = "Overloaded"
Else:
    Target = "Not overloaded"
End If
End Sub