@Pizzolati -
You have provided little context or detail. Based on the images and descriptions you have provided, I am not clear on what you're trying to do.
As I understand it, you have two Dataverse tables, "Employee" and "Employee/Machine Links". There is a one-to-many relationship between both tables from Employee (one) to Employee/Machine Links (Many).
The Primary Column in the Employee table is called "ID", and the related LookUp column in the "Employee and Employee/Machine Links" table is called "ID-Funcionario".
You have a Gallery control. I assume the Gallery is linked to the Employee table.
In the Gallery, I think you have embedded a Checkbox control. I assume the Default property of the Checkbox is bound to a "Yes/No" data type called "Active". I am assuming the code you have used is:
ThisItem.Ativo
What I think you're trying to do
If you want to disable the Checkbox if the ID column in the "Employee" table exists in the "Employee and Employee/Machine Links", you can apply the below to the DisplayMode property of the Checkbox control:
If (
IsBlank(
LookUp(
'Vínculos Funcionário/Máquina',
'ID- Funcionario'.ID = ThisItem.ID
)
),
DisplayMode.Edit,
DisplayMode.Disabled
)
If the above is not what you're trying to do, please provide further clarity.
