Hi Kaustubh,
You could use DaysBetween function in WebI.
So the formula would be like the following:-
If (DaysBetween(Currdate;Promise date)<=15) then Purchase Order
And for the second one:-
Pending Deliveries Where (DaysBetween(Promise date;Currdate)<15)
Let me know if the above works.
Regards,
Manpreet