Try this:

Code:
Declare Function ShellExecute Lib "shell32.dll" _
Alias "ShellExecuteA" (ByVal hwnd As Long, ByVal _
lpOperation As String, ByVal lpFile As String, ByVal _
lpParameters As String, ByVal lpDirectory As String, ByVal _
nShowCmd As Long) As Long

Public Const SW_MAXIMIZE = 3

ShellExecute Me.hwnd, vbNullString, "http://www.vb-world.net", vbNullString, "c:\", SW_MAXIMIZE