Just dug out our "House Rule #8". Had to chuckle, as it's quite complex... overly so.
House Rule AL8: "Disengage from Melee" Action is a Movement & Maneuver (MM) roll by each combatant, as follows:
1. The Disengaging combatant (Defender) rolls on the Movement & Maneuver table (GM to assign difficulty)
2. Add the Defender’s normal MM bonus + MeleeOB ÷ 5.
3. Result is the % of the maximum disengage distance (10'), rounded down to 0', 5' or 10'. Ie:
0-49 = 0' (failed to disengage)
51-99 = 5' (and may have disengaged - see below)
100+ = 10' (and may have disengaged - see below)
4. The Attacker makes an identical roll to see if he is able to counter the disengage action. If the Attacker's result is equal to or greater than the Defender's result, the defender FAILS his disengagement attempt.
I note that these rules allow melee to flow (movement-wise) as combatants jockey for position, so it has good flavour at least. If you attempt to disengage and fail, you might still be able to move 5-10' regardless, thus gaining a positional advantage perhaps.
These days I much prefer the D&D Opportunity Attack rules instead, as mentioned by others.