Changing Build Queue Order for a specific Project without affecting the other projects/system

I have multiple projects and I would like to change the order

1. Only for builds within a given project. Build jobs in other projects should retain their order.

So if ProjectA has 2 builds queue ProjectA-Build1 and ProjectA-Build2 

And ProjectB has 2 builds in the queue ProjectB-Build1 and ProjectB-Build2

Lets say the order using get builds is ProjectA-Build1 , ProjectB-Build2 , ProjectA-Build2 , ProjectB-Build1

Now if I want to change the order only for Project B such that it becomes like below. 

How do I do it using queueBuild to change order only for B
ProjectA-Build1 , ProjectB-Build1 , ProjectA-Build2 , ProjectB-Build2

2. When I apply the new queue order with only few builds then it cancels the remaining builds.
So if in the above example I use xml request with only ProjectB builds then it cancels ProjectA builds. I dont want to cancel any other builds.

3. Similarly if a after the get builds operation if a new build comes say ProjectA-Build3, then queuebuild will cancel that as well.

4. Also if a build completes before the queue order is applied then it re-adds a new one.

Any ideas on how to solve this case? I am wondering how in teamcity UI one can drag and drop to change the queue order. how does it do and which APIs and flow/steps does the teamcity UI uses?