Moving through pictures with picturebox and next previous buttons - vb.net

Question

I'm beginner level learner in using VB and currently I am trying create two buttons that will allow me to slide through pictures in an online folder. I need some kind of a way to change the image number in the URL so that the buttons will allow me to move through the pictures.
Private Sub Button4_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button4.Click
Dim pb1 As dispImg
pb1 = New dispImg()
pb1.picBox = PictureBox10
pb1.load("http://aipot.wowspace.org/imageapix.php?uid=iti2015&folderid=71&img=1&key=xxxxx")
End Sub
Private Sub Button5_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button5.Click
Dim pb1 As dispImg
pb1 = New dispImg()
pb1.picBox = PictureBox10
pb1.load("http://aipot.wowspace.org/imageapix.php?uid=iti2015&folderid=71&img=2&key=xxxxxxx")

Answer 1

Try this, notice the private variable.
Private _CurrentImage as Int32 = 1
Private Sub Button4_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button4.Click
CurrentImage += 1
Dim pb1 As dispImg
pb1 = New dispImg()
pb1.picBox = PictureBox10
pb1.load(string.format("http://aipot.wowspace.org/imageapix.php?uid=iti2015&folderid=71&img={0}&key=xxxxx",_CurrentImage ))
End Sub
Private Sub Button5_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button5.Click
CurrentImage += 1
Dim pb1 As dispImg
pb1 = New dispImg()
pb1.picBox = PictureBox10
pb1.loadstring.format("http://aipot.wowspace.org/imageapix.php?uid=iti2015&folderid=71&img={0}&key=xxxxx",_CurrentImage )))
End Sub
I am assuming Button4 is PREVIOUS and Button5 is NEXT. You will want to do some work to prevent numbers out of range but you can see how easy it is to Increment/Decrement a number and then stuff it in a string.