Validation Of Data Creating Problem In ASP Page

I got a ASP page where one can add a record or update any existing records.
As soon as a record is added it is appended to the existing records. With
this design user can check for erors in existing records or the added record.
Initially, there was ino data validation rule.

Now, as soon as I am putting
data validation via script, I cannot update the exisiting data as the
validation looks for empty space in the text boxes meant for adding data. Is
there any way, I can avoid this situation and can update existing records. If
this is possible, how does one validate the existing records.