Sorry, but this doesn't really make sense! First you say
"...by default it's checked..."
Then you say
"...But don't (sic) have default value..."
So, does it have a Default Value or not? If it doesn't have a Default Value...how do you expect it to have a Default Value?
And, as Ravinni suggested, what happens when the Checkbox is ticked has nothing to do with what occurs when the Form opens! If the Form opens to a New Record, set the formatting as you want it, which, if I read it correctly, is having WorkItems, SubProject and Hours all disabled.
Linq ;0)>
The problem with making anything foolproof...is that fools are so darn ingenious!
All posts/responses based on Access 2003/2007