How to Enable Disable Button Of list page using interaction class in ax 2012

Listpage interaction class: example

Listpage interaction class:( S3HrLeaveResquestListPageInteraction-interaction class,

S3HRLeaveRequestListPage-listpage name , DeleteCommandButton-button name(autodeclaration yes),

S3HRLeaveRequestListPage-listpage query, S3HRLeaveRequest_1-listpage table)

Create New Class & Write below code:=

public class S3HrLeaveResquestListPageInteraction extends SysListPageInteractionBase

{

    S3HRLeaveRequest S3HRLeaveRequest;

}

public void selectionChanged()

    {

S3HRLeaveRequest leaverequestCurrent = this.listPage().activeRecord(queryDataSourceStr(S3HRLeaveRequestListPage, S3HRLeaveRequest_1));

super();

 if(leaverequestCurrent.LeaveRequestApprovalStatus ==              S3HRLeaveRequestApproval::NotSubmitted)

        {

          this.listPage().actionPaneControlEnabled(formControlStr(S3HRLeaveRequestListPage,             DeleteCommandButton), true);

        }

        else

        {

            this.listPage().actionPaneControlEnabled(formControlStr(S3HRLeaveRequestListPage,             DeleteCommandButton), false);

        }

    }

Now extend this class to the form.