Hi @Rogan ,
Select the Data card or DataCardValue from the left pane , which you want to disable and write the formula in the DisplayMode property of the control.
Lets say you want to disable a field based on MachineStatus column , then use the below formula,
If(MachineStatus.Selected.Value="On",DisplayMode.Edit,DisplayMode.Disabled)
Please use DataCardValue property from the DataCard while you are disabling the field.
If this helps please give it a thumbs up and accept it as a solution.
Thanks,