I've been making a calendar system in excel to make phone booking for students (never say you know excel in work is the lesson I've learnt this week), it's all complete but an important part isn't done. A check to make sure that the Student Number has been entered into a calendar.

The string I'm need to search is Student ID which comes from C5 in main sheet. (6 digit number)

I then have 3 different work sheets for July, Aug, and Sept. Each has it's own calendar ranging from A1:Af100.

If it finds the student ID in one of the calendars then it needs to do nothing, but if it doesn't find them a warning message will pop up and end the function

MsgBox "Student ID not entered, please enter student ID into calendar"
End Function

I'm stuck which what function to use and getting one to work. Things have gotten stuck in infinity loops of nothing or just crash and goes to debug.