what is the best way of messaging between to application.

I am developing an inventory system which has two modules Manager's console and clerk's console,

manager sends a message to clerk to place a purchase order of goods specified in message this message appears in front of clerk.

i am doing this using timer control, which executes a piece of code after said interval, fetch data from purchase_order table and displays in front of clerk and timer starts again.

this works fine but consumes more processor's time.

suggest me more appropriate way to achieve the desired result.

Thanks & Regards