AT91 and three keys

Hi Guys,

i've got a little problem with my AT91 and some buttons, perhaps you can 
help me out of this. Thanks...so far!

've got thes lines of code:

AT91F_PIO_InterruptEnable(pPIO, BUT_left | BUT_right | BUT_menu);
AT91F_AIC_ConfigureIt 
(pAIC,??????,INTERRUPT_LEVEL_BUTLEFTRIGHT,AT91C_AIC_SRCTYPE_EXT_LOW_LEVE 
L,button_left_handler);
AT91F_PIO_InterruptEnable(pPIO,?????);
AT91F_AIC_EnableIt (pAIC, ???????);

What should i write at the "?" placeholder?
My names for the keys are : "BUT_left", "BUT_right", "BUT_menu"
But when i write one of these names at the place of the ? it's not 
working. Don't know why.

With googles help i found some other sides where their write 
"AT91C_ID_PIOA".
Is this right, correct?
And how can i decide which key is pressed? because for means this 
"AT91C_ID_PIOA" that an interrupt can occur somewhere of the PIO-Line, 
no matter where.

Any ideas?

Best regards