Without seeing how you set up your parameter here is how I would do it.
I woud use a yes/no visibility
Create the DRAFT text (as Text)
Now open the Family Types dialog and add a Yes/No parameter and name it Draft,
Make it either a type or instance depending how you want to use it and group it under Visibility.

Select the DRAFT text , and in properties under visible click on the Associate Family Parameters button and select the corresponding Draft parameter.

In the project when you create a new drawing sheet using the title block you can change the DRAFT status visibility by selecting the title block and ticking / unticking the Draft value (either as a type or instance depending how you set it up)

AJ.