Trend Formula

The Trend formula is used to forecast predicted growth or decline in most popularly sales figures of a business.
Theory:
=Trend(previous sales data range, previous months data range, new month number or cell reference)
Example:
=Trend($B$2:$B$13,$A$2:$A$12,C2)
For the formula above make sure you use absolute cell referencing with the dollars on both sides of the letters as shown, a part from the last cell reference being "C2" in this case. Then fill the formula down.
OR
=Trend($B$2:$B$13,$A$2:$A$12,13)
For the formula above make sure you use absolute cell referencing with the dollars on both sides of the letters as shown, a part from the last part which is just a number in this case "13". This paticular formula using the number 13 and not a cell reference is only useful for single next month prediction.
The table below is a sample data set. NB: T is for Trend Forecast and mn is for Month.
A       B          C        D
mn  sales    T.mn   T.sales
1      8685    13       5625
2      7865    14       5437
3      9765    15       5248
4      4455    16       5060
5      7865    17       4871
6      2334    18       4683
7      9876    19       4494
8      5647    20       4306
9      7864    21       4117
10    3456    22       3929
11    9823    23       3740
12    4567    24       3552