Something like this:
CREATE FUNCTION GetOvertimeHours
(
@OverHours FLOAT
)
RETURNS FLOAT
AS
BEGIN
DECLARE @Hours FLOAT
IF (@OverHours <= 0.0) RETURN 0.0
IF (@OverHours <= 1.0) RETURN @OverHours * 1.5
SET @OverHours = @OverHours - 1.0
SET @Hours = 1.5 + @OverHours * 2.0
RETURN @Hours
END
GO