Программа не может выйти из цикла - VB

Private Sub Command1_Click()
Dim k, m, n As Integer
Dim x, x1, T As Single
x1 = Text1.Text
m = Text2.Text
[COLOR="lime"]'The first Option[/COLOR]
If Option1.Value = True Then
T = 0: k = n: x = x1
For k = n To m
T = T + (2 * k + x)
Next k
Label13.Caption = "Used For/Next Method"
Text5.Text = "T = " & Round(T, 2)
End If
[COLOR="Lime"]'The second Option[/COLOR]
If Option2.Value = True Then
T = 0: k = n: x = x1
Do While k <= m
T = T + (2 * k + x)
k = k + n
Loop
Label13.Caption = "Used Do While/Loop"
Text5.Text = "T = " & Round(T, 2)
End If
End Sub