changing comint-input-ring-file-name in process in shell

[Seb]

Hi,

A program that runs in shell mode uses a local history file.  Therefore,
I'd like to set `comint-input-ring-file-name' to that file.  I use the
program by doing "M-x shell", and then start the program in the shell
buffer by typing its name and hitting ENTER.  The program's prompt
replaces the shell's at this point.  I thought that subsequently
evaluating the following in the shell buffer would allow me to cycle
through the local history file:

(setq comint-input-ring-file-name
      "/path/to/local/.bash_history"))

However, cycling with "M-p" or "M-n" cycles the input through the
initial `comint-input-ring-file-name' set by the shell buffer, in my
case ~/.bash_history since I'm using bash.  Doing "C-h v
comint-input-ring-file-name" does show the new value
("/path/to/loca/.bash_history"), so I don't understand what is going
on.  Any help would be appreciated.

Cheers,

-- 
Seb