Keypad Scanning Question, help reqd.

I have a 3x4 keypad connected to portB of a pic16c74 and written the basic code
which will jump to the interrupt vector whenever any key is pressed. I then will
read portB and move the value to another register. thats the code so far,

What I want to do are the following.

a) discover which key was pressed
b) use each key to call a different subroutine

My problem is how to implement the key descrimination as there is no compare
command, I think I need to XORLW ? but what then etc,
I also need to implement a table read, don't I ?

Any help and direction appreciated

Email to  - ashsparky@clara.net - thanx for your time