ON ENTER Event for Input field of the table

Hi Expert,

i have a table and in that table there is one input field which has associated with the search help.Once user press F4 help for that input field ,currently he is getting the list of possible values..

Problem Detail:-

user press Cancel on the list of values and then enter data for that field manually and try to save data.It is giving error message that the field is blank.

Whether i have do coding in the ON ENTER event for that input field.

Please suggest .

Thanks

Mahesh