Dim Winkel1 As Double, Winkel2 As Double
'1. Quadrant
If X1 >= 0 And Y1 >= 0 Then
  If X1 = 0 Then Winkel1 = Atn(1) * 2
  If X1 <> 0 Then Winkel1 = Atn(Y1 / X1)
End If
'2. Quadrant
If X1 < 0 And Y1 >= 0 Then Winkel1 = Atn(1) * 4 - Atn(Y1 / -X1)
'3. Quadrant
If X1 < 0 And Y1 < 0 Then Winkel1 = Atn(1) * 4 + Atn(Y1 / X1)
'4. Quadrant
If X1 >= 0 And Y1 < 0 Then
  If X1 = 0 Then Winkel1 = Atn(1) * 6
  If X1 <> 0 Then Winkel1 = Atn(1) * 8 - Atn(-Y1 / X1)
End If
 
'1. Quadrant
If X2 >= 0 And Y2 >= 0 Then
  If X2 = 0 Then Winkel2 = Atn(1) * 2
  If X2 <> 0 Then Winkel2 = Atn(Y2 / X2)
End If
'2. Quadrant
If X2 < 0 And Y2 >= 0 Then Winkel2 = Atn(1) * 4 - Atn(Y2 / -X2)
'3. Quadrant
If X2 < 0 And Y2 < 0 Then Winkel2 = Atn(1) * 4 + Atn(Y2 / X2)
'4. Quadrant
If X2 >= 0 And Y2 < 0 Then
  If X2 = 0 Then Winkel2 = Atn(1) * 6
  If X2 <> 0 Then Winkel2 = Atn(1) * 8 - Atn(-Y2 / X2)
End If
 
'Winkeldifferenz >= 180°
If Abs(Winkel1 - Winkel2) >= Atn(1) * 4 Then
  If Abs(Winkel1) > Abs(Winkel2) Then
    Winkel1 = Winkel1 - Atn(1) * 8 * Sgn(Winkel1)
  Else
    Winkel2 = Winkel2 - Atn(1) * 8 * Sgn(Winkel2)
  End If
End If
If Winkel2 > Winkel1 Then Label1 = "Links"
If Winkel2 < Winkel1 Then Label1 = "Rechts"
If Winkel2 = Winkel1 Or Abs(Winkel2 - Winkel1) = Atn(1) * 4 Then Label1 = _
  "Geradeaus"