Amount of concurrent calls in the in- and outbound route

It would be great if i can set the amount of concurrent calls in the in- and outbound route. 

In- and outbound route using the same trunk (the only one i have) with 4 channels. The inbound route shouldn't be able to handle more than two calls at one time. The same with the outbound route -> only 2 concurrent calls.

2 calls in + 2 calls out = 4 total concurrent calls.