SQL & PL/SQL

hi,

I am quite new to PL SQL. I need to select data from a table , process the dates (which are in string format) and then copy data to another table. I am using cursor , processing each row at a time. if the string data (to be converted into date) is not in proper fomat ( sometimes N/A, sometimes blank) then sql raises an exception where i assign default date.
when the exception is raised how to continue with the next row. 'coz when an excpetion is occuring the whole procedure stops and does not move to next table row.

Can anyone help me with this?
Thanks.