8. The system of claim 7 , wherein each of the one or more UI controls is of a type that is natively supported by the PIM.
7. A system for rendering a custom user interface (UI) form in a personal information manager (PIM), the system comprising: a design computer comprising at least one processor that executes instructions in a memory in communication with the at least one processor, the design computer further comprising: a forms generator module configured to execute on the design computer and to generate a native UI form specification for a PIM, the native UI form specification containing one or more UI controls from a form markup file containing markup that specifies the design of a custom UI form by providing a layout of the one or more UI controls, data binding information specifying internal and external data sources from which contents of the one or more UI controls will be populated, and event subscription information specifying logic to be executed by a custom event handler when a particular event is generated by the one or more UI controls; and a runtime computer comprising at least one processor that executes instructions in a memory in communication with the at least one processor, the runtime computer further comprising: a PIM application configured to execute on the runtime computer, to store the native UI form specification in a PIM form storage, and to render the native UI form specification to display the custom UI form by incorporating the custom UI form in a specific region of a native UI displayed by the PIM; and a forms runtime engine module configured to execute on the runtime computer, to bind a data source to each of the one or more UI controls on the custom UI form having the data binding information specified in the form markup file, and to subscribe to an event for each of the one or more UI controls on the custom UI form having the event subscription information to a custom event handler for the event generated by the UI control specified in the form markup file.