VBscript code behind custom form in Exchange public folder is not running in Outlook 2010

In Outlook 2010, the default behavior was changed to prevent scripts from running in public folders. To re-enable this behavior in Outlook, follow these steps:

• Click File, and then click Options.
• In the list of categories, click Trust Center, and then click Trust Center Settings.
• In the Trust Center, click the E-mail Security category.
• Click to enable Allow script in Public Folders.

For more information read the following article from Microsoft