Sub SortDown(ByRef A())
    Dim t As Boolean
    Dim i, j As Long
    Dim a0 As Variant
    t = True
    i = LBound(A)
    While t
        t = False
        i = i +  1 
        For j = UBound(A) To i Step - 1 
            If A(j) < A(j -  1 ) Then
                a0 = A(j)
                A(j) = A(j -  1 )
                A(j -  1 ) = a0
                t = True
            End If
        Next
    Wend
End Sub


Sub test()

Dim C As Variant
C = Range("A1:D5")

Dim i, j As Long
ReDim c0(LBound(C,  1 ) To UBound(C,  1 ))

For j = LBound(C,  2 ) To UBound(C,  2 )
    For i = LBound(C,  1 ) To UBound(C,  1 )
        c0(i) = C(i, j)
    Next
    SortDown c0
    For i = LBound(C,  1 ) To UBound(C,  1 )
        C(i, j) = c0(i)
    Next
Next
Range("A11:D15") = C

End Sub

Function Xnext(Xprev, x, n) As Double
    Xnext = Xprev * x ^  2  / (n * (n -  1 ))
End Function

Function Y(x, d) As Double
    Y =  1 
    X0 =  1 
    n =  0 
    Do
        n = n +  2 
        Xn = Xnext(X0, x, n)
        If Abs(Xn - X0) > d Then
            Y = Y - Xn
            X0 = Xn
        Else
            Exit Do
        End If
    Loop
End Function

Sub test()
    
    d =  10  ^ - 10 
    
    i =  1 
    For x = - 0 . 5  To  0 . 5  + d Step  0 . 1 
       Cells(i,  1 ) = x
       Cells(i,  2 ) = Y(x, d)
       i = i +  1 
    Next
    
End Sub