Form Personalization - Make field required based on LOV selection

Question

Newbie here.
I am trying to make a field required based on the selection of the LOV that is next to it. Having a heck of a time with it.
The form i am working on is the Sub Invenntory form that you get to via Organization Items. We want the subinvnetory field to be manditory when subinv is selected from the LOV in the sources tab.
here is what i have so far:
CONDITION
Trigger Event: WHEN-VALIDATE-RECORD
Trigger Obj: ITEM_SUBINVENTORIES
Condition: ${item.item_subinventories.SOURCE_TYPE.value} = 3
Action
Type: Property
Object Type: Item
Target Object: ITEM_SUBINVENTORIES.SOURCE_SUBINVENTORY
Property Name: REQUIRED
Value: TRUE
The problem seems to be that i can't get the field to be required. It shows up yellow but still allows me to save w/ the field being blank.

Answer 1

I do not know about the particular form that you are trying to personalize, but whenever I have created a condition, it has usually been in the following syntax:
:BLOCK_NAME.FIELD_NAME = 'VALUE'
For example, :MTL_SYSTEM_ITEMS.PRIMARY_UNIT_OF_MEASURE_MIR = 'SEAT'
Yours seems to be very much different from mine, but then again, I am not technical so I cannot comment intelligently on that aspect.
May be that is the problem.
Also, once you get it to work, you might want to also add a condition where the field is turned to un-required when the SOURCE_TYPE is NOT 3.