编写了一段程序中间有一个调用API的函数，但是运行感觉到有问题产生。由于是新手，所以没有找到错误是什么

Private Declare Sub Sleep Lib "kernel32" Alias "sleep" (ByVal dwMilliseconds As Long)


Private Sub form_click()
    DrawWidth = 1
    For j = 1 To 20
        Cls
        For i = 0 To 6000 Step 100
            Sleep 40
            DoEvents
            Line (i, 1200)-(2800, 2900), 2
            Sleep 40
        Next i
    Next j

End Sub
也就是这么几行代码，大家帮帮忙。谢谢