Sub macros6()
Dim x(15) As Single
Dim first, last, n, i As Integer

For i = 1 To 15
x(i) = Cells(i, 1)
Next i

Call otbor(x)

End Sub

Function otbor(g() As Single) As Single
    For i = 1 To 15
        If g(i) < 0 Then
        last = i
        Cells(1, 3) = last
        End If
    Next i
    For i = 15 To 1 Step -1
        If g(i) < 0 Then
        first = i
        Cells(1, 2) = first
        End If
    Next i
End Function