how to lock/unlock certain cells
 

I have a worksheet with about 400 rows. Each row is for a specific product
and contains "specifications". The remainder of my workbook uses the lookup
function to populate from this worksheet. I need to "lock" this sheet so
that when one row is being edited no other row can accidentally be changed.
I have to clue where to start with this. Any suggestions???

thanks so much in advance!
--
AJ