INDIRECT and real-time question

[Pavel Shevchenko <pavel telemetry-investments com>]

Hi, All:

In our company we are going to use gnumeric instead of Applix, so
I am going to implement proper INDIRECT() function and real-time interface.

I was able to create some real-time interface based on sample datasource 
example plugin, but it has one problem: there is no way to stop updating spreadsheet
when user remove real-time function call. The same problem exists with the 
dependency problem for INDIRECT() function. It is relatively simple
to add dependency to the cell for which this function refer, but problem is
how to remove this dependency.

So, now I am going to implement some way to register/unregister 
callbacks for the cell changes, which will be called just after user
finish editing cell, but before formula parsing. 

In case of INDIRECT() function it will allow to register callbacks 
which will remove added dependency for the reffered cell. In the 
case of real-time fuction it will allow to stop updating spreadsheet
after user removed real-time fuction call.

I will appreciate any comments/suggestions to this plan.

Thanks,
Pavel.