PyHTHEME = OpenThemeData(hwnd, pszClassList
)
Open the theme data for the specified HWND and 
semi-colon separated list of class names. 
OpenThemeData() will try each class name, one at 
a time, and use the first matching theme info 
found.  If a match is found, a theme handle 
to the data is returned.  If no match is found, 
a "NULL" handle is returned. 
When the window is destroyed or a WM_THEMECHANGED 
msg is received, _winxptheme::CloseThemeData should be 
called to close the theme handle.
Parameters
hwnd : int
Window handle of the control/window to be themedpszClassList : string
Class name (or list of names) to match to theme data 
section.  if the list contains more than one name, 
the names are tested one at a time for a match. 
If a match is found, OpenThemeData() returns a 
theme handle associated with the matching class. 
This param is a list (instead of just a single 
class name) to provide the class an opportunity 
to get the "best" match between the class and 
the current theme.  For example, a button might 
pass L"OkButton, Button" if its ID=ID_OK.  If 
the current theme has an entry for OkButton, 
that will be used.  Otherwise, we fall back on 
the normal Button entry.