Validation in Close problem button

Hi Experts,

                 We need to implement the below functionality in the close problem button in problem management. 

We have a field named Resolution in problem management. The requirement is when we are clicking on the close problem button it should check whether the Resolution field is filled or not. If it is not filled then it should give a message like " Please specify the Resolution" , otherwise the problem should get close directly.

I have tried by giving messages and conditions in process but it is showing errors.

Please help me to implement this functionality.

Thanks & Regards,

Sandhu Mol