VB.NET Modify a Bitmap in a function Call - vb.net

Question

I'm trying to modify a bitmap in a function call.
Without the function call I can do
'MyBitMap - an existing bitmap of what I want to modify
Using NewBitMap as BitMap = MyBitMap.Clone 'make copy
Dim G as Graphics = Graphics.FromImage(MyBitMap) 'Draw graphics to MyBitMap
G.Clear(color.white) 'Clear image
G.DrawImage(NewBitMap, -10, 0) 'Shift Image to left 10
PictureBox1.Image = MyBitMap
End Using
works fine no memmory overflow or anything
In a sub it works fine
Sub BMScroll_S(BM as BitMap, dx as integer, dy as integer)
using BMtemp as BitMap = BM.Clone
Dim G as Graphics = Graphics.FromImage(BM)
G.Clear(color.white)
G.DrawImage(BMTemp, dx, dy)
End Using
End Sub
Call BMScroll_S(MyBitMap, -10, 0)
PictureBox1.Image = MyBitMap
works fine, but if I try to create a Function to return a Bitmap
Function BMScroll_F(BM as BitMap, dx as integer, dy as integer) as Bitmap
BMScroll_F = New Bitmap(BM)
Using BMtemp As Bitmap = BM.Clone
Dim G As Graphics = Graphics.FromImage(BMScroll_F)
G.Clear(Color.White)
G.DrawImage(BMtemp, dx, dy)
BM.Dispose()
End Using
End Function
MyBitMap=BMScroll_F(MyBitMap, -10, 0)
PictureBox1.Image = MyBitMap
here I have a Memory Leak and after more and more iterations, it will crash.
I suppose in the function call you are returning a bitmap as well as the fact that BitMaps are passed ByRef so they will continue to exist. I thought BM.Dispose might get rid of it - but it doesn't. I not quite sure how to solve my memory leak (if it is in fact due to my supposition). Granted, I could continue on with the Subroutine but I'd like to know how to solve this problem any way. Any help would be appreciated.