trapping mouse in picture box

Yes, in fact, I'll give you an working example that you can use.

Public Declare Function KeepKursor Lib "user32" _
Alias "ClipCursor" (lpRect As Any) As Long
Public Type RECT
        Left As Long
        Top As Long
        Right As Long
        Bottom As Long
End Type

Sub CursorR(PictureB As PictureBox)
  Dim rrt As Rect
  rrt.Left = PictureB.Left
  rrt.Top = PictureB.Top
  rrt.Right = PictureB.Left + Picture1.Width
  rrt.Bottom = PictureB.Top + Picture1.Height
  KeepKursor(rrt)
End Sub

Also, if you want to learn, reserch ClipCursor.