picturebox1 name = PictOuter
picturebox2 name = PictInner

Dim pos As String
Dim bos As String

pos = Format(x / PictOuter.Width * 100, "0")
bos = Format(y / PictOuter.Height * 100, "0")

PictInner.Left = PictOuter.Width * pos / 100
PictInner.Top = PictOuter.Height * bos / 100
PictInner.Visible = True

Private Sub PictOuter_MouseDown(Button As Integer, Shift As Integer, X As Single, Y As Single)

    PictInner.Left = X
    PictInner.Top = Y

End Sub