Extra Unit For Each Unit Created

[-Albi]

I'm new to modding and I've currently been creating a new civ to play. One of the ideas I had was to create a unique building which allows an extra cavalry unit (both light and heavy) to be created when one unit is trained along with some other yield modifiers.

I've managed to get the building into the game as well as the yield modifiers but I'm completely stumped as to how I go about the extra cavalry unit. I've looked at the modifiers and I'm unable to find anything, however I know the modifier exists as I've been able to create an extra naval unit in the vanilla game.

I'm not very experienced in xml so any help towards making this possible would be greatly appreciated

 

[kingchris20]

I’m not near a computer right now, but Scythia has that ability with their Saka horse archers, so you should be able to copy from that setup.

 

[-Albi]

I’m not near a computer right now, but Scythia has that ability with their Saka horse archers, so you should be able to copy from that setup.

I think this has pointed me in the right direction, I had a look at Scythia and I think I found the modifier that I needed. However, after testing I was unsuccessful in creating an extra unit.
This is the code that I have at the moment.

Spoiler :

<Modifiers>
        <Row>
            <ModifierId>LOTR_ROHIRRIC_STABLE_EXTRALIGHTCAVALRY</ModifierId>
            <ModifierType>MODIFIER_PLAYER_UNITS_ADJUST_EXTRA_UNIT_COPY_TAG</ModifierType>
        </Row>
        <Row>
            <ModifierId>LOTR_ROHIRRIC_STABLE_EXTRAHEAVYCAVALRY</ModifierId>
            <ModifierType>MODIFIER_PLAYER_UNITS_ADJUST_EXTRA_UNIT_COPY_TAG</ModifierType>
        </Row>
    </Modifiers>
   
   

    <ModifierArguments>
        <Row>
            <ModifierId>LOTR_ROHIRRIC_STABLE_EXTRALIGHTCAVALRY</ModifierId>
            <Name>Tag</Name>
            <Value>CLASS_LIGHT_CAVALRY</Value>
        </Row>
        <Row>
            <ModifierId>LOTR_ROHIRRIC_STABLE_EXTRALIGHTCAVALRY</ModifierId>
            <Name>Amount</Name>
            <Value>1</Value>
        </Row>
        <Row>
            <ModifierId>LOTR_ROHIRRIC_STABLE_EXTRAHEAVYCAVALRY</ModifierId>
            <Name>Tag</Name>
            <Value>CLASS_HEAVY_CAVALRY</Value>
        </Row>
        <Row>
            <ModifierId>LOTR_ROHIRRIC_STABLE_EXTRAHEAVYCAVALRY</ModifierId>
            <Name>Amount</Name>
            <Value>1</Value>
        </Row>
    </ModifierArguments>

 

[criZp]

<BuildingModifiers>
<BuildingType>
<ModifierId>

you don't have this code