How to close a dialog box by 2 ways (user/ext.cmd)?

["CHABAL David" <david chabal c-s fr>]

Hello,

I develop an GTK application launching external commands with
g_spawn_async_with_pipes.
A GtkDialog box is displayed during the background command execution, it
had one button
"Kill" (the pid of the command is given by g_spawn_async_with_pipe).

So, I want to close this GtkDialogBox:
- when the background command is done (normal termination)
or
- when the user cancel the command (kill button).

I have done many tests (launching the ext. cmd in a thread sending a
response
with gtk_dialog_response...) but in some cases I have gtk error messages
like GTK_IS_DIALOG(dialog) failed. I suppose there is a concurrence
between
the 2 close ways ?

Somebody could help me ?

TIA,
David