How to find out the given date contain this week are not?

Hi all,

i have one requirement give the soluiton?

s.no        date

1        20141103

2        20141105

3        20141109

4        20141112

5        20141117

Name          date

  abc        20141107

  def         20141109

i entered the date of  'abc'  in selection-screen check the date in given date. if you not date in database  generate the error message?

how to in code?