[otrs] Customized Field Validation via JavaScript Functions?

Is there any way to add custom JavaScipt functions to the UI? Would this require a new theme? Would it be possible to hook in my own JS file to the "minifier" to accomplish this? I have two use cases in mind: 1. An agent sets a ticket to a status like "waiting for vendor". I would then like to require that the free text field for vendor reference IDs has a value. 2. Some agents would prefer to input time with "tokens", like "1:30" for 1.5 hours, or 5m for five minutes. A JS function could handle these translations. Any ideas? Hugh