What you have should work because once you set Enabled=false, the validators are disabled.
Now you will see the browser posting back to the server, but the result will be the same - the validator still works!
Right now, the button does nothing, besides posting back if the page is valid.
Here setting validate All Properties = true is the important part.
If it is false then it will perform only the first default validation 'Required' and it will not check other Validation for the properties like 'Regularexpression', 'Range', etc.