How to write interrupt priority in C for PIC16F727

[helloleong]

The PIC16F727 does not have interrupt priority it self

So my code have 3 interrupt, and the simplified code are as below

void interrupt isr(void)
{
     if (RBIE && RBIF && (~PORTB & 0x30)){...}

     if (SSPIE && SSPIF) { SSPIF = 0;}

     if (T0IE && T0IF)
     {
         //If the processor servicing Timer 0 interrupt,
         //and at the same time PORTB interrupt occur.

         //How can I immediately exit this if statement
         //and service PORTB interrupt immediately?
         ...
     }
}

I have to set PORTB interrupt as high priority to capture the wiegand data.
Some time the 1st wiegand data was miss.
If I take out the Timer 0 interrupt if statement, all wiegand data are able to be fully capture.
So how can I immediately exit this if statement and service PORTB interrupt immediately?

Thank you very much.