Microsoft Outlook Task Forms
Here are some of the oddities related to customized task forms in Outlook. If you are aware of these from the beginning, you'll spend less time beating your head against the wall.
You cannot customize the first page of the Task form.
Outlook does not include a version of the drop-down calendar control for developer use on custom forms. See To add a date-time picker control to an Outlook form.
The Outlook object model does not expose any properties related to the Keep an updated copy of this task on my task list and Send me a status report when this task is complete check boxes on tasks being assigned to other users. My conclusion is that Outlook takes the user's choices in these check boxes and applies them on the fly to the hidden attachment that goes out as part of the task request, leaving no way to set those options programmatically.
At least in some versions, if you hide the first page of the Task form and put the Message/Notes control on a custom page, the Copy and Paste menu commands and toolbar buttons remain enabled, but do not function inside the Message/Notes control. However, the Ctrl+C and Ctrl+V shortcut keys do work.
In Outlook 2000 at least (maybe in other versions, too), the Forward action is disabled on a custom task's right-click context menu, but still appears on the Actions menu.
If you disable the first page of a task form, when users click the Assign button on your custom form, they won't see the To box for filling in the assignee.
If you bind a control to the Company field, changing the data in that control does not fire the PropertyChange or CustomPropertyChange event. The workaround is to create a custom formula property with the formula [Company] and bind that property to the control. You should then get a CustomPropertyChange event. (Thanks to Outlook MVP Jay Harlow for documenting this quirk.)
There is no simple way to link a master task (in other words, a project) with subtasks. One approach is to use a Contact form for the project and take advantage of the Links collection for linking tasks to it. Outlook MVP Ken Slovak, in his Professional Microsoft Outlook 2007 book, presents a complete add-in project for hierarchical task management.
You cannot add your own values to the Status drop-down list.
OOutlook VBA help indicates that the Owner property is always read/write. This isn't true. It's read/write only if the task is stored in an Exchange Server public folder. If it's in a mailbox or Personal Folders file, you can change the value of Owner, but when you try to save the item, Outlook gives you an error message.
You cannot capture the Send event on a customized task form. When you add recipients to a task and send the resulting task request, Outlook does not send the original task. Instead, it creates a new Task Request item and sends that item.
Embedded objects, shortcuts, etc. in task items cannot be launched after the item is saved and reopened. There is no known workaround.