The easiest way to move a picturebox ina straight line is to chang PictureBox's coordinates every second. All you have to do is to insert a Timer Object onto the form. the code is as follows

Sub Timer1_Timer()
Picture1.Left = Picture1.Left + 120
'Say that the X coordinate of the farthest point of the
'form is 4440. Then we want it to stop

If Picture1.Left = 4440 Then
Timer1.Enabled = False
End If

End Sub