How can i add forcecountdown? after deferrals

can anyone help? we are trying to give timer for the last deferal

I’m not sure I understand the question. Force Countdown for what?
The way deferrals work is you have x number of deferrals. When you defer, it ends the script with, iirc 60002 error code. It relies on whatever software deployment system to relaunch the application (most times SCCM/MECM or similar). The deferrals remaining reduces each time. Once zero deferrals remain, It will begin the installation with no chance to defer. At that point it would leverage whatever countdowns you have implemented. For instance, a 5 minute countdown to close open applications, etc.