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I am trying to create a monitor profile for my Sony P234/B using
Pantone ColorVision's ColorPlus 1.0.1 with little luck. The process
seems to run well, and a profile is created and placed in the proper
folder, made the default, but it doesn't do anything. That is, it has
no effect on the screen image and all of the numerical values are
unchanged.

Have any of you had success calibrating this monitor by creating a
monitor profile and, if so, with what software?

I believe this software method has even been discontinued by the
manufacturer.
The only effective monitor calibration requires use of an external device to
measure the output from your screen.
They all require hardware adjustments of the monitor's controls (brightness,
contrast, RGB values) to optimize the screen initially. Then a series of
color tones of known values is generated and the actual output of your
screen is measured and recorded to create a profile that is transferred into
your video driver and is set automatically for you.
Color management is more difficult with LCD panels than CRTs but can be
done. I presume the p234 has the necessary manual controls for calibration.