Fusion HCM Composer - Add a validation

Content

Hello ,

This is the use case: First, A new pending worker is uploaded throught FBL. Then you have to assign for this pending worker a Manager. Finally, it should be converted to employee. The thing is, How can I put a validation of assigning a manager BEFORE converting it to employee. Composer? Aplication composer?.A popup or something?. Clicking the convert botton? 

If yes, how?.

Thanks in advance 

Agustin Celentano