How to Detect if Sprite is going Up or Down - vb.net

Question

I Use the following code to detect if a sprite should be going up or down and the response
If (pos.Y + 100) >= Sprite.BottomY Then
Going_up = True
pos.Y = Sprite.BottomY - 130
End If
If pos.Y <= Sprite.TopY Then
Going_up = False
pos.Y = Sprite.TopY - 1
Vel.Y = 3
End If
then
If Going_up Then
Vel.Y -= CSng(gameTime.ElapsedGameTime.TotalMilliseconds / 40)
pos.Y -= Vel.Y
Else
Vel.Y += CSng(gameTime.ElapsedGameTime.TotalMilliseconds / 40)
pos.Y += Vel.Y
End If
Sprite.velocity = Vel
Sprite.position = pos
but it's pretty terrible. It only works when the sprite starts at the top, and when I want to change the BottomY and TopY, it just starts glitching. What is a better to detect if the sprite should be going up or down?

Answer 1

Can you not just do:
If (Vel.Y > 0) Then
Going_up = True
' Do rest of up code
Else If (Vel.Y < 0) Then
Going_up = False
' Do rest of not going up code
End If

Answer 2

Something that might help is utilizing a getter and setter like this:
Essentially, you could create a tempX and tempY. Every 100ms compare the sprite's current properties with the temp variables.
Dim tempX As Double
Dim tempY As Double
While True
tempY = sprite.GetY()
If gameTime.ElapsedGameTime.TotalMilliseconds Mod 100 = 0 Then 'or something to sample the game time
If sprite.Vel.Y > tempY Then
Going_up = True
Else
Going_up = False
End If
End IF
End While
So you're sort of taking a sample of your game board to create approximate reference points that you can compare the actual value to. Hope that helps!
-sf