Hi @Perrault,
Have you solved your problem?
Do you want to disable the button in the Power Apps based on a specific fields value?
Could you please tell me that the column type of the field, is it a Yes/No type or a Text type?
Actually, how to set the DisplayMode property of the button depends on what the column type is.
As @anibra mentioned that if the column type is a Yes/No column, you could try the formula provided.
If the column type is a Choice or a Text, please modify as below:
If(ThisItem.Column.Value= "Yes", DisplayMode.Disabled, DisplayMode.Edit) // Assume it is a Choice type
If(ThisItem.Column= "Yes", DisplayMode.Disabled, DisplayMode.Edit) // Assume it is a Text type