Each record must be tagged on creation with ACCOUNT NAME (not Username) Username can be changed by the user...AccountName cannot.
Create an "AccountName" field and set it to Autoenter "Get(AccountName)"
Then adjust the privilege set for the users under "Record Privileges"...Custom Privileges...View...Limited....Field::AccountName = Get (AccountName)
You will also want to put something like a "show mine" button on the layout to restrict the found set to their records...otherwise they will be wading through many records that all say <<no access>>.
See "Editing record access privileges" in FileMaker Help and check out this particular sub section: "Entering a formula for limiting access on a record-by-record basis" for a description of how to set this up.
ok ..bt how to show particular records only..i mean how to show records according to a/c name/username
If you set up the record level Access control to which I referred in my previous post, any find your script performs will automatically filter out the records for which the users privilege set does not grant access.
Here's a script that finds all records on a given layout, relying on RLA to automatically omt the records to which the current user is not granted access:
Enter Find Mode 
Set Field [YourTable::PrimaryKey ; "*"]
Set Error Capture [on]
In place of YourTable::PrimaryKey, you can refer to any field in the current layout's table that is never empty of data.
bt when i set the privilege then they does nt allow to create new record..in create record i just set yes stilll...
That would indicate a need to modify the options selected for that privilege set...
Since the autoenter function is in play, the user would need to not only create, but also modify the record (I think).
how to modify privilege set ..i mean i alreadyy set it to limited access ....now wat to do??
There are privilege set optionst that will enable the user to do what they need to do. And you'll need to check the "Available Menu Commands" drop down as well since it can prevent a user from doing what they need if it is set to too strict a setting.
But we have no idea what options you have or have not selected for your privilege set. You might upload a few screen shots of the dialog boxes involved so that we can see what options you have selected in order to advise you on what needs changing.