Excel

_Carter16 

You might use the following VBA function:

Function SumNotStrikethrough(rng As Range) As Double
    Dim cel As Range
    Application.Volatile
    For Each cel In rng
        If Not cel.Font.Strikethrough Then
            SumNotStrikethrough = SumNotStrikethrough + Val(cel.Value)
        End If
    Next cel
End Function

Use like this in a cell formula:

=SumNotStrikethrough(A2:A10)

Warning: applying strikethrough to a cell or removing it will not cause the result of the formula to be updated automatically. It will be updated the next time Excel recalculates any formula. You can force this by pressing F9.