VB运行时没有响应，求大神帮忙

Private Sub Command1_Click()
Dim z1, z2, z3, z4 As Integer
Dim i As Single
Dim X, Y As Single
Dim t1, t2 As Single
Dim p As String
List1.Clear
t1 = (Abs(X - Int(X + 0.5)) <= 0.02 And Abs(z1 - Int(z1 + 0.5)) <= 0.001 _
And Abs(z2 - Int(z2 + 0.5)) <= 0.001 And Abs(z3 - Int(z3 + 0.5)) <= 0.001 _
And Abs(z4 - Int(z4 + 0.5)) <= 0.001)
For z1 = 70 To 120
For z2 = 70 To 120
For z3 = 70 To 120
For z4 = 70 To 120
X = z1 * z3
Y = z2 * z4
If (z1 * z3) / (z2 * z4) = 0.7853983 Then
End If
p = Format(z1, "@@@") & Format(z2, "@@@@") & Format(z3, "@@@@") & Format(z4, "@@@@")
List1.AddItem p

  Next
Next

Next
Next
End Sub

循环次数太多了。一共循环了50×50×50×50次。