Disabling Other Page

I have a login form. when user logs in, user is transferring randomly an Exam page.
these pages're(ExamA.asp and ExamB.asp)

Question is :
if user transferred to ExamA.asp how can i disable to enter ExamB.asp ?
(there is no link in ExamA.asp to ExamB.asp. only changing url in the address bar.)

here is my login from code :

strSQL="Select Exam from Exam"
set Exam=conn.execute(strSQL)
Stat=cint(Exam("Exam"))

if Stat=1 then

sqlUp="update Exam set Exam=2"
conn.execute(sqlUp)
response.redirect ("ExamB.asp")

elseif Stat=2 then

sqlUp1="update Exam set Exam=1"
conn.execute(sqlUp1)
response.redirect ("ExamA.asp")
end if