how to write a conditional statement in SQL-Server with Where statement?

I have an attendancesheet project. I want to say something like this:

    create procedure ClockINorOUT
    @InputDate nvarchar(50),
    @inputName nvarchar(50)

    as

    IF tbl_attendancesheet.clockOut is null,
    and tbl_attendancesheet.clockIn is null
    insert into  tbl_attendancesheet(clockIn) values @inputName where name=@inputName,

    IF tbl_attendancesheet.clockOut is null,
    and tbl_attendancesheet.clockIn is not null
    insert into  tbl_attendancesheet(clockOut) values @inputName where name=@inputName,