[otrs] RFI | How to create a new field as like Time Units | Help Needed

Hello, I just wanted to create a new field as like Time Units in OTRS 3.0, whenever I update the ticket and enter the hours / minutes / seconds so that it keeps on adding it, just as same as Time Units field work. Trying to do it from couple of days now and have no luck on this, would appreciate if someone can help me with this. Thanks, Him