Sorry, come again?
Do you mean this:
You have a user who needs to directly open a datasheet but no-one else needs (or is allowed) to open the datasheet? All others besides this one user MUST go through a form?
If that is what you meant, then look into ByOwner (or is it AsOwner? It is a property of the query, I think...) queries as the basis for your form. Give the OTHER users no permission to the table, but give yourself permission. Then build a query that shows YOU as the query owner. Then build the form based on your query and using the ByOwner option. Allow the special user permission to the table.
What this does is allow the special user and you to open the table. The other users MUST use another method because they don't have direct Open permissions. But the form that uses the ByOwner query can open the table because when the query runs, it runs as its owner (YOU) and has permissions of the owner (YOU). Of course, the FORM then becomes the enforcer of usage rules. Make sure the form is carefully coded to prevent anyone from doing anything they shouldn't do.
To complete the circle, you should probably make the query hidden so that no one will be overly tempted to open it directly.
