You can do this with coding, im not sure if this is right, but here we go:
#include <pspctrl.h>
#include <pspkernel.h>
#include <pspdebug.h>
int main() {
sceCtrlData pad;
if(buttons.pad & PSP_CTRL_CROSS)
(buttons.pad & PSP_CTRL_CIRCLE)
Yeah, Its kinda wierd, cause it is not really a program, but you could probably change the
firmware a little. I think just doing a hardware mod would be easier, unless your really good
at C.