Compare two object of associated entity

Hello Experts I've entity A associated to B via one to many association. Now, I want to 1- select one object of A from dropdown 2- and compare two corresponding objects of B by selecting them from dropdown   can anyone suggest approach, I tried reference selector but as soon as I make selection in 2nd drop down 1st updates with same value which is right thing for the object. 
1 answers

If you need to previous value for the reference selector, add an onchange event to the reference selector that triggers a microflow. In the microflow perform a database retrieve action with the xpath like:

[id = $inputobject]

to retrieve the value of the object from the database.

Now you can compare the value of the association in a decision, to see if the value has been changed.

If you need to compare data on entity B then retrieve the entity B from the inputobject and from the databaseobject and perform the needed compares.

Hope this helps in finding a solution for your requirement.