How to add inverse of delay in simulink

Hello,

I am trying to simulate a pneumatic pipeline, where I know the flow and pressure at the output and wish to determine the inlet pressure. In case the inlet pressure is known and outlet pressure is to be determined, it can be done by addition of an attenuation coeffeicient for the flow and delay transfer function. I was thinking of using similar approach for my problem. So, I need something like inverse of delay. I cannot use the transfer function approach here as it would give an unstable pole if I take inverse of delay transfer function. So, I would like to know if there is any other approach that I may take.

Thanks,

Shilpesh