Where is the problem?

Good luck trying to get pbp to set a bit var where you need it be
use a byte and place it in access space if you have to

enabling the timer1 interrupt and not servicing it will not work well


Code:
#CONFIG  __config _CONFIG1, _FOSC_INTOSC & _WDTE_OFF & _PWRTE_ON & _MCLRE_OFF & _CP_OFF & _CPD_OFF & _BOREN_ON & _CLKOUTEN_OFF & _IESO_ON & _FCMEN_ON
  __config _CONFIG2, _WRT_OFF & _PLLEN_ON & _STVREN_ON & _BORV_19 & _LVP_OFF
#ENDCONFIG


DEFINE INTHAND INT
DEFINE NO_CLRWDT 1
DEFINE OSC 4
OSCCON = %01101010


TRISA   =    %011000   ; RA4 input for battery measurement, RA3 input on change, rest output
ANSELA  =    0     ; ADC Disable
OPTION_REG = %10000111 ; Disable internal pull-ups, TMR0 On, prescaller to 256


FVRCON  =    %10011000 ; Internal reference to 2048mV


CM1CON0 =    %10100110 ; Comparator output to C1OUT, switch on LED if voltage is below ref. 2,048V
CM1CON1 =    %00100001 ; C1IN1- pin is RA4, comparator voltage input, C1IN1+ positive input to FVR set to 2,048V


LATA    =    %000001   ; init state of pin RA0 and RA1, LEDs connected to these pins


T1CON = %00110001      ; TMR1 On, prescaller 1:8, Fosc/4
INTCON = %11001000     ; Enable GIE, PEIE, IOCIE
PIE1.0 = 0             ; DISable TMR1IE OVerflow interrupt 
IOCAN.3 = 1            ; Enable RA3 negative edge OnChange interrupt


Switch var BYTE  $7f  SYSTEM 
 Switch = 0 




; ------------  With TMR1 and interrupt, oscilator 4MHz ---------------
Main:
if porta.3=0  and switch=1 then         
LATA = LATA ^ %100000
pressed:
pause 20
if porta.3=0 then pressed   ; if the button is still pressed loop and wait for release
Switch=0
endif
goto main 


 asm
INT
 banksel IOCAF
 btfsc IOCAF,3
 bsf Switch,0                      ; set bit0 in Switch to 1
 bcf IOCAF,3
 RETFIE
endasm