=SUM(SMALL(INDEX($F5:AH5,MATCH(TRUE,COLUMN($F5:AH5)=LARGE(NOT(ISBLANK($F5:AH5))*COLUMN($F5:AH5),4),0)):AH5,{1,2,3}))/3

=(sum(FourValuesRange) - max(FourValuesRange))/(count(FourValuesRange)-1)

=(SUM(($F5:AH5)*(COLUMN($F5:AH5)>LARGE((COLUMN($F5:AH5))*(NOT(ISBLANK($F5:AH5))),4+1)))-MAX(($F5:AH5)*(COLUMN($F5:AH5)>LARGE((COLUMN($F5:AH5))*(NOT(ISBLANK($F5:AH5))),4+1))))/3

Public Function MovAverage(rIn As Range) As Double
    Dim wf As WorksheetFunction, M As Long
    Dim zum As Double
    Dim it(1 To 4)
    Set wf = Application.WorksheetFunction
    N = rIn.Row
    M = rIn.Columns.Count + rIn.Column - 1
    j = 1
    zum = 0
    For i = M To 1 Step -1
        v = Cells(N, i).Value
        If v <> 0 And v <> "" Then
            it(j) = v
            zum = zum + v
            j = j + 1
            If j = 5 Then GoTo NextPart
        End If
    Next i

NextPart:

    MovAverage = (zum - wf.Max(it(1), it(2), it(3), it(4))) / 3

End Function