Form method problem

Hi to all 

(i write the below code in from lave in modified method )

 In the table every record has signOnDate and SignOffDate .my requirement is if i give  the AsOnDate , it check SingnonDate and signnOf date  and give the records. i write the below code for that . it is not working good . any one plz help mee 

select firstOnly ProjId,CrewId,SignOnDate,SignOffDate from CrewMovementLine

        where CrewMovementLine.ProjId      == PersonnelOnBoardTable.ProjId

        &&    CrewMovementLine.CrewId      == PersonnelOnBoardLine.EmployeeID

        &&    CrewMovementLine.SignOnDate  >= PersonnelOnBoardTable.AsOnDate

        &&    CrewMovementLine.SignOffDate <= PersonnelOnBoardTable.AsOnDate;