How to check date from less than and greater than

Question

How to check date from less than and greater than with example

Ex:I have Two Date First One : 01/10/2015 and Second One : 10/10/2015 .

Then I insert Any Middle date like : 02/10/2015 , 05/10/2015 etc... Than Show Me Message That Product Allready

booking . PlZ Answer This Querry