maintain data from drop down menus
 

I have created an Excel (2007) form for workers to use where some columns
have drop down menus. Many people are cutting and pasting from an older,
similar version of the form (still 2007) which doesn't contain the same
options as in the new drop down menu. I would like to know how to "lock" the
cell to where the people cannot simply cut and paste other data and input
that data into those cells. Thank you in advance for your help.