start and end date validation for searches [SOLVED]

[eluser]tim1965[/eluser]
Sorry i have just re-read my original post and i did not make clear probably the most important point.
These fields are optional , they only become required if they are filled in. i.e. end_date is only required if start_date is filled in, likewise start_date is mandatory if end_date is entered, likewise the third field is optional until filled in in which case i need to check that start and end date are completed to properly run the query. If no data is entered into any fields then i dont need to apply the check.
Apologies i should have made clear, my fault for trying to do two things at once.