"redraw","cell" is definitely a valid command for the matrix object.
Like Bill, I am puzzled as to why you are using a timer. I don't see any reason why it should be necessary.
Since you are using a timer, I think the problem is the local variable, vCellClicked. That variable only exists in the original procedure -- you can't use it in the timer code. The timer code is a separate procedure, so it doesn't share local variables with any other procedure, including the procedure where it is defined. So your timer code has an error. However, timer code doesn't report errors with an alert, because that could easily cause a situation where Panorama locked up because it was generating errors once per second (or whatever the timer frequency is). It should have displayed a notification of the error, but maybe you have notifications disabled, either globally or for just Panorama.
My first choice would be to get rid of the time, and just use objectaction directly. That should be the simplest solution.
If you want to use the timer, you could make vCellClicked into a windowglobal variable. Or, you could embed it into the timer code like this:
That would be my second choice.