Option Explicit

Private Type SplinePoint
  X  As Single
  Y  As Single
End Type

Dim Quit As Boolean

Dim CSP As SplinePoint
Dim SP(50) As SplinePoint
Dim TP(100) As SplinePoint

Dim CurrentPoint As Integer
Dim CurrentPos As Single

Private Sub Start_Cmd_Click()
  Dim n As Long

  DrawWidth = 3
  Quit = False
  CurrentPos = 0

  TP(0).X = SP(0).X
  TP(0).Y = SP(0).Y
  For n = 1 To CurrentPoint - 2
    TP(n * 2 - 1).X = SP(n).X + (SP(n - 1).X - SP(n + 1).X) / 5
    TP(n * 2 - 1).Y = SP(n).Y + (SP(n - 1).Y - SP(n + 1).Y) / 5

    TP(n * 2).X = SP(n).X - (SP(n - 1).X - SP(n + 1).X) / 5
    TP(n * 2).Y = SP(n).Y - (SP(n - 1).Y - SP(n + 1).Y) / 5
  Next
  TP(n * 2 - 1).X = SP(CurrentPoint - 1).X
  TP(n * 2 - 1).Y = SP(CurrentPoint - 1).Y

  Do
    DoEvents
    CurrentPos = CurrentPos + 0.001
    subGetSplinePoint SP(Int(CurrentPos)), _
        TP(Int(CurrentPos) * 2), TP(Int(CurrentPos) * 2 + 1), _
        SP(Int(CurrentPos) + 1), CurrentPos - Int(CurrentPos), CSP
    PSet (CSP.X, CSP.Y)

    If CurrentPos > CurrentPoint - 1 Then Quit = True
  Loop Until Quit = True
End Sub

Private Sub subGetSplinePoint(P1 As SplinePoint, _
      P2 As SplinePoint, P3 As SplinePoint, P4 As SplinePoint, _
      u As Single, P As SplinePoint)

  P.X = P1.X * (1 - u) ^ 3 + _
        P2.X * 3 * u * (1 - u) ^ 2 + _
        P3.X * 3 * u ^ 2 * (1 - u) + _
        P4.X * u ^ 3
  P.Y = P1.Y * (1 - u) ^ 3 + _
        P2.Y * 3 * u * (1 - u) ^ 2 + _
        P3.Y * 3 * u ^ 2 * (1 - u) + _
        P4.Y * u ^ 3
End Sub

Private Sub Form_MouseUp(Button As Integer, Shift As Integer, _
      X As Single, Y As Single)
  SP(CurrentPoint).X = X
  SP(CurrentPoint).Y = Y
  DrawWidth = 3
  PSet (X, Y)
  CurrentPoint = CurrentPoint + 1
  If CurrentPoint = 2 Then Start_Cmd.Enabled = True
End Sub

Private Sub Form_QueryUnload(Cancel As Integer, _
      UnloadMode As Integer)
  Quit = True
End Sub