Probe to read quadrature encoder with DT_INT need help

[phoenix_1]

These code count pulses from one pin of quadrature encoder good and fast.
It use RB0 INT very good.
Now I need idea to implement full reading quadrature encoder A and B inputs with count of pulses and direction indication..
Encoder is with 500 pulses per full revolution.
How - need idea..?
Procesor 16F877 @ 20MHz

define OSC 20
DEFINE HSER_RCSTA 90h ' Enable serial port & continuous receive
DEFINE HSER_TXSTA 24h ' Enable transmit, BRGH = 1
DEFINE HSER_SPBRG 64  ' 19200 Baud @ 20MHz, 0.16%
DEFINE HSER_CLROERR 1 ' Clear overflow automatically

ADCON1 = 7                       
TRISB = %00000011
a var word
a = 0
INTCON = %10010000 ; Enable INTE RB0 interrupt $90 
INCLUDE "DT_INTS-14.bas" 
INCLUDE "ReEnterPBP.bas" 
ASM
INT_LIST macro ; IntSource, Label, Type, ResetFlag?
    INT_Handler INT_INT,    _TEST,  PBP, yes
    endm
    INT_CREATE ; Creates the interrupt processor
ENDASM

Main: 
if a >= 5000 then
a = 0
endif
hserout [ dec a ]
pause 100
GOTO Main

'---[INT_INT - interrupt handler]------------------------------------------

TEST:
a = a + 1
@   INT_RETURN

Regards Robert