I am not sure how to write the code in ms access vba, but how would you think
for saving visio drawing before closing access application, and next time,
for opening the saved drawing.
In case of vb6 project, the visio drawing can be saved by SaveAsEx method,
FileName = Me.Dir1.Path & "\" & Me.Text1.Text
MDIForm1.DrawingControl1.Src = ""
MDIForm1.DrawingControl1.Document.SaveAsEx FileName, &H2