Не могу разобраться с циклами(

Option Explicit
Private Sub Комманда1_Click()
Dim SUM
Randomize
Dim X(1 To 6) As Single
Dim J As Byte
For J = 1 To 6
 X(J) = CSng(InputBox("Элемент №  " & J, "Ввод данных", Int(10 * Rnd)))
 SUM = SUM + F(X(J))
  Next J
 MsgBox SUM, 64, "Результат"
End Sub
 Function F(X)
 Dim c, b, z
 c = -0.5
 b = -3 * c ^ 2
 z = c ^ 2 - 3 * b
 F = Cos(z) - 6 * X
 End Function

Option Explicit
Private Sub Комманда1_Click()
Dim SUM
Randomize
Dim X As Single
Dim J As Byte
For J = 1 To 6
 X = CSng(InputBox("Элемент №  " & J, "Ввод данных", Int(10 * Rnd)))
 SUM = SUM + F(X)
  Next J
 MsgBox SUM, 64, "Результат"
End Sub
 Function F(X)
 Dim c, b, z
 c = -0.5
 b = -3 * c ^ 2
 z = c ^ 2 - 3 * b
 F = Cos(z) - 6 * X
 End Function

Private Sub Form_Load()
Dim x As Single, z As Single, b As Single, c As Single
Dim i As Integer
Dim Sum As Single
c = -0.5
b = -3 * c ^ 2
z = c ^ 2 - 3 * b
For i = 1 To 6
    x = InputBox("Input a value for x")
    Sum = Sum + (Cos(z) - 6 * x)
Next i
MsgBox Sum
End Sub

Private Sub Form_Load()
Dim Y As Single
Dim x As Single
Dim n As Integer
Dim i As Integer
Dim Sum As Single
n = InputBox("Input a value for n")
x = InputBox("Input a value for x")
Sum = x / 1 - Cos(x)
For i = 2 To n
    Sum = Sum + (x / (i - 1) - Cos(i * x))
Next i
MsgBox Sum
End Sub