A general purpose Pulse Delay with a variable delay could lead to the situation where the order of events (rising/falling edges) is reversed when the delay time is reduced. PLECS therefore does not provide such a block.
If the rate of change of the input signal and delay period are subject to certain constraints, then a workable solution could be possible. Could you better describe exactly the kind of signal you are delaying? Is it binary or real-valued? How does the signal input change relative to the delay period? Does the input have a fixed sample time?
Assuming this relates to your previous question about a phase-shift modulator (https://forum.plexim.com/7873/transfer-the-code-in-matlab-to-plecs),
you can use the turn-on delay blocks along with additional logic to implement a variable phase delay. See the "Switch Delay" block in "Subsystem 1".
For a C-Script implementation - see this previous answer which includes an example of a variable turn-on delay with comments. You can build on this to implement your desired functionality. (https://forum.plexim.com/4509/create-delay-with-c-script
If you would like to make a more general purpose discrete delay, then you should direct your question towards email@example.com.