Simulation Device... Keyed Peak Detector

I want to build an ideal device for use in PSpice simulations, a Keyed
Peak Detector...

Finds the maximum peak value of an input voltage while it's enabled
("keyed"), and "dumps"/outputs zero when not enabled.

Any ideas?

(Ideal elements)

                                        ...Jim Thompson
-- 
| James E.Thompson, P.E.                           |    mens     |
| Analog Innovations, Inc.                         |     et      |
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