How to add a custom activity in SuiteCRM.

Hi All!

In suitecrm we have calls,meetings,notes,emails for Activities. further when this activities are held it will show in the history subpanel else if they are planned it will show up in the activities subpanel.
I want to know how to create a custom activity like(Ex: call__) for suiteCRM. is it possible conceptually within suitecrm.
Please guide me to develop this.