Folder access security

i have a windows NT 4 workstaion, there are 2 users for that pc, Say Users are A & B

there are 2 folders named A-data & B-data
i want each user access there own data folder not the other one
Eg: user “A” should not be able to acceess “B-data” folder

i dont want to create different user profiles as each time logging off and on is not possible

is there any way i can set this security