System should not pick reserved stock

Dear, MM Experts, i am sd Guy

i want to block Reserved stock while creating sales order

ex: 150 qty kept In reserve for customer , Total plant stock 1000

Now if user created sales order with 150 qty Normally system will pick 150 qty From reserved stock ( 412 E)

Here user requirement system should not pick Reserved stock 150   Bz in critical situation is there Like non production of stock

ex total stock in the plant 175 only there ( ex 155,180,200,170) So in this  situation only system will pick Reserved stock 150

Otherwise Reserved stock should be in reserved place only bz if is not like this always we have keep stock in reserve

Thanks