This doesn't really make sense. All users should have their own front ends
(on the local machine, and should not be sharing a single front end over the
network). The only way to do this is that I know of is to have a table with
a single record per form that you want to do this to and write a flag to the
table and check it before opening the form.
And then you need to deal with that flag remaining set when someone's
program and/or computer bombs out.
If only one particular user (i.e. John only; not Mary or George or Henry
or Anita or....) is to be allowed to open it, you could do something with
security that only allows that one person.
