Question: About variable delay

Hello,

These days I thought a question:how to creat a variable delay?

As illustrated in Fig.1, if delay time T is constant, then the output is y(t)=u(t-T), so we can use a block named "Pade Delay" in maplesim to achieve our purpose.As shown in Fig.3.

If delay time is variable,namely,T(t), then the output is y(t)=u(t-T(t)), as illustrated in Fig.2. But in maplesim,no variable delay block.

So let's simplify the question:set the delay is increasing at a constant rate of 0.1sec/sec, namely, T(t)=0.1*t. Then substitute  T(t)=0.1*t to y(t)=u(t-T(t)), so the result is y(t)=u(t-0.1*t)=u(0.9*t).

Does my deduction right?

Further more, is there any way to creat a variable delay block with its delay time T(t) is variable, for examle,T(t)=0.1*t ?  or write a procedure?

Thank you!