Check tables in B/X or BECMI.
1)  To evade = you must be able to move faster than the pursuers & know where you are going.  This is done in Combat Rounds. Note that the pursuers may opt to pursue over a period of days in some situations. In this case, roll once per day.

Evasion Attempts = (Shadow Elves, pg 18, Vikings, PHB, pg 17). Eluding pursuit by use of hiding, dodging, use of false trails, throwing food at a hungry pursuer, or otherwise out-guessing the pursuer. Can also run away at double speed for up to 10 combat rounds. Take a +2 mod when used.

(A)  If the players run, monsters will pursue on 1D20 = 9+ using these mods:
-2 if any monster is slain, hits do not count
+2 if no monsters have been hit
+3 if the monsters are hunting the players

(B)  Both sides would initially move at the rate of their slowest member.
- If not faster, you may drop things.  There is a 50% chance pursuing non- intelligent monsters will stop to eat any food you toss away.  Intelligent monsters have a 50% chance of stopping to look at any treasure you toss away.

- Anything else may stop pursuit on 1D6 = 4+, while they investigate

- Magical & mindless monsters will always pursue, they ignore dropped stuff..

- Faster members may pursue while slower ones follow along

(C)  Continue pursuit, after every 5 rounds, roll again to determine if the monsters continue to pursue.

Roll 2D6 = 9+ to continue the pursuit.  Monsters will rarely pursue longer than 1-2 hours unless you have something very valuable.  Use these mods:

-2 if any monster is slain, hits do not count
+2 if no monsters have been hit
+2 if the monsters outnumber you
+3 if the monsters are hunting the players