Reference the MSDN under Optional arguments and overloading  for VB.NET (Jan2003)

Here is optional link for Jan2003 release of MSDN if it helps
ms-help://MS.VSCC/MS.MSDNQTR.2003JAN.1033/vbcn7/html/vaconConsiderationsOverload\
ingProcedures.htm

I'm no VB expert and there is too much info  in MSDN to quote here. Check it out.