Want to detect either pc is in sleep mode or not

Question

• I am creating a website in asp.net. and i want to detect my pc screen mood is on/off.
• when the monitor screen is turn off i want to user redirect to the login page.
  
• is there any way to detect monitore's screen mood or sleep mood to chcek user is active or not on the system?

thanks in advance

and sorry for poor english