How to update decision box field based on two criteria

How to update decision box field based on two criteria

Hi, 

I am trying to update a decision box field which will show an assessment record as "overdue" if it has not been marked. I want this to be based on if the due date is before the current date and the marked box is false. I am trying to use this code but I'm getting an error statement:

if(Marked == false && Marking_due_on < zoho.currentdate)
{
input Overdue == true


Any help would be much appreciated!