Restrict to create Travel Expense report without having corresponding Travel request

Hi All,

Is there any standard settings or custom, through which we can restrcit the user from creating a Travel Expense Report without having a corresponding Travel Request. If there is no travel request exists, then system should popup a message that "Create a Travel Request first".

And also there is one more point to capture personal expenses through Travel Management system. In this case Travel Request is not required. I am planning to create one more schema as "Personal Expenses" to capture this.

So for one schema Travel request is mandatory & for another it is not mandatory.

Please help.

Regards,

Daniel