hide unhide button depending on cell value

Hi you'll

I have a workbook for teachers to fill out grades for their students. The main sheet has all the names and subjets. The rest of the sheets are named by the cells which have the names of the students and the subjects in it (every student and every subject has its own sheet) . This is done by a calculate event. These sheets are veryhidden when no student/subject name is entered. On the main sheet I have buttons (from forms control) that, when clicked, go to the sheet from that student. I have been looking for some code that hides the button when no name is entered (no name means sheet hidden, means when button clicked error pops up since the sheet is hidden) and to unhide when a name is entered.
Thanks in advance for any help offered.
MarcoAUA