Detecting Estrus' locked player mode?

[Fredas]

Trying to figure out how to tell when Estrus enters into its locked-player mode.  Why?  Because there's about a six second delay between casting the spell on self and anything actually happening, and this causes my own mod to be slightly out of sync.  (The course of events seems to be: You cast spell, six second wait, you get frozen and animation begins, another six second wait, freecam mode begins.)  Rather than putting in a blind six-second delay and hoping it always takes that long, I'd much prefer being able to tell when the player gets frozen at the start of the actual animation.

 

.IsLocked and .IsDisabled evidently don't change.  So they don't fit the bill.