How to make the reading for indicating of deflection of the line

[Tamgovb]

Hi All

I have something like this

Option Explicit
    Dim Ruch As Boolean
    Dim intDlugosc As Integer

Private Sub Form_MouseDown(Button As Integer, Shift As Integer, X As Single, Y As Single)
    intDlugosc = intDlugosc + 1
    Load Line1(intDlugosc)
    Line1(intDlugosc).X1 = X
    Line1(intDlugosc).Y1 = Y
    Ruch = True
End Sub

Private Sub Form_MouseMove(Button As Integer, Shift As Integer, X As Single, Y As Single)
    If Ruch Then
        Line1(intDlugosc).X2 = X
        Line1(intDlugosc).Y2 = Y
        Line1(intDlugosc).Visible = True
    End If
End Sub

Private Sub Form_MouseUp(Button As Integer, Shift As Integer, X As Single, Y As Single)
    Ruch = False
End Sub

How to be visible with my code, I can draw a some the straight of the line - for example : in the vertical.
Until I have pressed mouse's button I can this line to incline under any angle (in initial point of line).
Now I want to read the value of this angle - suffice for me only in the range since 0 to 180 degrees, how to make it?

Any suggestions, maybe a some lines of the code, thanks in advance