Reservation from Sales Line

Hi all,
I have one query of reserving quantity from Sales Line.
I want to reserve quantity from one screen that will be Sales Line.
Here on this screen user want to have Total Availability and Reserved Quantity of that Item shown on every line.

User want that they ll enter the quantity to reserve on sales line and that quantity will be reserved. How to achieve that.

Basically if anybody can explain the full process of Reservation. What all I have to consider in doing this from this functionality.

Thanks and Regards.