How to set up prescaler on ISR to a certain interval in microseconds?

I have a PIC18F87J11 device and I'm supposed to create:
1) a high-priority ISR that's supposed to be triggered every 100ms
2) a low-priority ISR that's supposed to be triggered every 10ms

I have a basic knowledge about configuring a pre-scaler, in example for Timer0, it's

movlw b'00000010'
movwf T0CON

as manual page reads, this should configure Timer0 to 16bit counter, pre-scaler 1:8 (device's manual page 179). The problem is, I don't know how to determine the correct pre-scaler settings when I want 100ms intervals. Any help appreciated.

EDIT:
Okay, now I realize that I probably have way less idea about what I'm doing then I thought. I can't find relevant information in manual (and I'm sure it is there). I need to set up Timer0 to 100ms and Timer1 to 10ms.

Solution

Here are you have ISR high-priority initiation rutine for TMR0.

At very begining of your MCPU initiation code you must define...

;Init TMR0 as 8 bit timer, overflow every 1024 CPU cycles if TMRxPrescaler4 is set
;{
TMRxPrescaler2      equ 0
TMRxPrescaler4      equ 1
TMRxPrescaler8      equ 2
TMRxPrescaler16     equ 3
TMRxPrescaler32     equ 4
TMRxPrescaler64     equ 5
TMRxPrescaler128    equ 6
TMRxPrescaler256    equ 7

    movlw   (1<<TMR0ON) + (1<<T08BIT) + TMRxPrescaler4
    movwf   T0CON
    bsf INTCON, TMR0IE       ;enable TMR0 overflow interrupt 
;};

After MCPU initiation don't forget to switch on interrupts...

    bsf     INTCON, GIE

ISR rutine:

ISR
    bcf INTCON, TMR0IF              ;demask TMR0 overflow interrupt
;your ISR code
    retfie  1

In ISR rutune count numbers of TMR0 overflows, for 10MHz CPU clock: 10000000 / 4 / 1024 = 2441.4 overflows for one second.

I recommend that you are using only one ISR rutine where you handle both events.