Append Counter Variable To Field Name

Hi all,

I have a table with fields name Days1, Days2, Days3 - I am trying to use a loop in conjunction with a counter to identify each of these fields - I can't quite get the correct syntax and it is driving me crazy!!!

Here's the proc:

WHILE @Counter < 4
BEGIN

SELECT @AppointmentsCount = COUNT(tbl_SurgerySlot.SurgerySlotKey)
FROM tbl_SurgerySlot INNER JOIN
tbl_SurgerySlotDescription ON tbl_SurgerySlot.PracticeCode = tbl_SurgerySlotDescription.PracticeCode AND
tbl_SurgerySlot.Label = tbl_SurgerySlotDescription.Label LEFT OUTER JOIN
tbl_Appointment ON tbl_SurgerySlot.SurgerySlotKey = tbl_Appointment.SurgerySlotKey AND
tbl_SurgerySlot.ExtractDate = tbl_Appointment.ExtractDate
WHERE (tbl_SurgerySlot.ExtractDate = @ExtractDate) AND (tbl_Appointment.AppointmentKey IS NULL) AND
(tbl_SurgerySlot.StartTime > @DateFrom) AND (tbl_SurgerySlot.StartTime < @DateTo) AND (tbl_SurgerySlotDescription.IsBookable = 1)

SET @FieldName = 'Days' + CONVERT(VARCHAR(20),@Counter)

INSERT INTO tmp_Availability (@FieldName)
VALUES (@AppointmentsCount)

SET @DateTo = DATEADD(Day,1,@DateTo)

--Increment the loop counter
SET @Counter = @Counter + 1

When I run the above the follwoing message is displayed:

Server: Msg 208, Level 16, State 3, Line 36
Invalid object name 'tmp_Availability'.

The object IS valid so I'm lost....