I would like to know how each event handler works and when it triggers. And also which event is best to populate the customized Unbound field. I have been using Rowselected event for Unbound field. According to some sources, Rowselected is used only for the UI controls.
So, In which event I should use to calculate and populate the Unbound field with out using PXFormula like Attributes
This should get you started.
See the sequence of entries from the link above for more detail on the order of events. For example here is the image from Sequence of Events: Update of a Data Record:
For unbound fields you should use the PXUnboundFormulaAttribute or the FieldSelecting or RowSelecting events for calculated values.