Two things. Make sure your slides
integer is outside the Tick event. Also, make sure to cover the condition of "equals", which your code doesn't check for, so slides
is constantly falling into the "else" category and setting back to zero. That is, when slides
equals 20, you don't have a condition that satisfies it, so it resets to zero.
Private slides As Integer
Private Sub Timer1_Tick(sender As Object, e As EventArgs) Handles Timer1.Tick
slides += 10
If slides <= 20 Then
PictureBox1.Left += 10
ElseIf slides > 20 AndAlso slides <= 40 Then
PictureBox1.Top += 10
ElseIf slides > 40 AndAlso slides <= 60 Then
PictureBox1.Left -= 10
ElseIf slides > 60 AndAlso slides <= 80 Then
PictureBox1.Top -= 10
Else
slides = 0
End If
End Sub