• Open a webpage:

dde execute iexplore WWW_OpenURL http://www.tcl.tk/

• In a new window: WWW_OpenURLNewWindow
• open a file: WWW_ShowFile

dde execute iexplore WWW_ShowFile C:/Program%20Files/....

• dde request iexplore WWW_GetWindowInfo 1

• WWW_Activate - brings most recent window to front.
• WWW_Exit - causes the top-most window of iexplorer to close.
• WWW_ListWindows - returns (number of active windows - 1) as a DWORD

See http://support.microsoft.com/kb/q160957/