Issue in ESS Portal leave application

Hi

we are  facing an issue with 2nd level approval .

Once the first level  leave approval is done if employee is changing the leave dates , it is directly going to 2nd level approver , but it should go again to first level approver .

How to send this to first level approver again (Once dates are changed ) or how to disable the edit activity in webdynpro once first level approver is completed .