You will need to set the autoredraw property of the picturebox to true before drawing, then refresh the picturebox, then use the savepicture function, like this:

Code:
picture1.autoredraw = true

'Do Drawing
'...

picture1.refresh
savepicture picture1.image, filename
Offcourse change picture1 in the name of the picturebox you are drawing on.

-Shell-