[syslinux] multiple comboot files?

[Bryan E. Chafy]

Is there a way for isolinux/syslinux to execute a list of comboot files
immediately at startup, and only once?
I have a bunch of small comboot .com files that I want to batch run immediately,
then after that do a
DISPLAY boot.msg

similar in some ways to an autoexec.bat.
For example:

DEFAULT mycd
APPEND ramdisk_size=100000 init=/etc/init lang=us ....
TIMEOUT 300

ONSTARTUP mybatch <- ???

LABEL mybatch   <- start this right away, but not related to DEFAUT or TIMEOUT
KERNEL myisr1.com
KERNEL myisr2.com
KERNEL myisr3.com


Also, in my case some of these comboot files are ISRs, so they need to stay resident
in some way, even just before transferring the IP to a kernel.
(they work individually already, but just one at any given time and crash
at the point when a kernel is loading into memory).
Is there a way to ensure a loaded comboot file stays resident and
the memory it uses wont get overwritten, for example even when loading a kernel
or by yet another comboot file?
If the comboot file could be instructed to load in a reserved high segment,
or even just after the BDA, the
available memory reported by the bios (INT 12 and INT 15 AX=E820h)
could be reduced, but I dont know if this approach will work under syslinux.
>From the source, it looks like comboot_seg is 4000, right in the middle.

Also, related to the first question, if I want to disable one of my
ISR's just before loading a kernel, I need to execute another smaller comboot
file to restore the IVT and other hardware registers.
When some action is exceuted, by say a keyword label, or default,
I would like to be able to load that smaller comboot file, followed by
the loading of the kernel, basically like above, but not at startup.

For example:

LABEL mycd
KERNEL endisr1.com
KERNEL endisr2.com
KERNEL linux24
APPEND ramdisk_size=100000 init=/etc/init lang=us ....

Any help appreciated.