Database

create procedure MyProcedure
@c1 int,
@c2 int,
@c3 int,
@c4 int,
@c5 int,
@c6 int,
@c7 int
as begin
  set nocount off
 
  update MyTable set c5 = @c5, c6 = @c6, c7 = @c7
     where c1 = @c1
     and c2 = @c2
     and c3 = @c3
     and c4 = @c4
 
  if (@@ROWCOUNT = 0) begin
     insert into MyTable (c1, c2, c3, c4, c5, c6, c7)
       values (@c1, @c2, @c3, @c4, @c5, @c6, @c7)
  end

  return (0)
end

CREATE TRIGGER InsertIntoSummarySells
INSTEAD OF INSERT
AS
BEGIN
  DECLARE @C1 INT -- or whatever type it is
  DECLARE @C2 INT -- ...
  ... -- And so on, with the parameters

  SET NOCOUNT ON
  UPDATE tblSummarySells
  SET C5 = @C5,
  C6 = @C6,
  C7 = @C7
  WHERE
    C1 = @C1 AND C2 = @C2 AND C3 = @C3 AND C4 = @C4

  IF @@ROWCOUNT  = 0
  BEGIN
    INSERT INTO tblSummarySells ....
  END
END

DECLARE @Mth1 varchar(5)
DECLARE @Yr1 varchar(5)
DECLARE @Mth2 varchar(5)
DECLARE @Yr2 varchar(5)

SET @Mth1 = '5'
SET @Yr1 = '2007'
SET @Mth2 = '8'
SET @Yr2 = '2007'

DtCol >= Convert(datetime, '01/' + @Mth1 + '/' + @yr1, 103) 
   AND DtCol < DateAdd(m, 1, Convert(datetime, '01/' + @Mth2 + '/' + @yr2, 103))