When graphing data I normally allow for insertion of new data, creating formulas that can be copied and pasted for calculations. Thus, I insert new lines, and copy formulas for calculations for new data, say weekly.
Using the Trend function, I can now add the trend, extending my graph with this function. However, while I can insert new lines, then copy and pasting formulas for new data; trend data is typically at end point of the graphing data range. When inserting, this is the last line or lines of the graph, and doesn't change, or get copied because insertion occurs from the line previous to the endpoint for inclusion in ranges, especially when graphing or using certain functions. Anyone who uses this, knows that inserting between a range before it's last end cell point, extends the range in calculations. Often we include range functions here for that reason. However, TREND is an exception, as insertion occurs before the TREND data calculation.

The end point trend uses the last 7 days. and since this by use would be to collect the last 7 days of data, and extrapolate the next 7 days. This is one line of code, and sits ON the endpoint, as the last piece(s) of graphing information. Ex: Data (Date/Data) A1:B7 with Trend using this range, but displays x days after A7 or A8:A8+x for date, and B8:B8+x for Trend data in B8 specifying A8:A8+x range for x values.

As mentioned, typically one inserts an extra 7 days of data, or whatever is needed to expand data set. By inserting 7 lines at A8; A8 is moved which includes the range, and expands it. This allows the graphing ranges to expand, and the entire sheet follows it.

However, this doesn't work for the Trend function, as it is for the following week, and is an interpolated extrapolation. Because it is the endpoint of a range: Insertion occurs within the end points, and by choice, this allows for new data; however, trend because of it's relative reference, and being outside of the insertion, retains (by design) and is desired in all other functions of the sheet and formulas, it retains the "relative" value of the points selected. Normally, this is desirable and good, and wanted behavior. I acknowledge it. However, Trending is an exception. There are times when one would like it to retain a selection of data that is both relative, but fixed. Relative in that it would retain, in this case, the last 7 days, but fixed in that those last 7 days change when inserting new data within a range. We want the trend, in this case, to select that last 7 days, and so it is a fixed, relative position.

By inserting 7 lines, the Trend could, if opted to so do, should when expanding the data range, allow it to remain fixed to a relative position to it's current location. Like when programming in VBA, and using the Range function. ex: Range("I94").Select So, perhaps I should just knuckle down and learn to use the relative commands; however, I do not use this normally on spreadsheets, and my understanding is that would be require extensive modification. Unless things have changed, I'm not aware of certain VBA functions being available in spreadsheet mode as insertion into coding cells. (How foolish is this; I don't know, or I'd fix it.) To quote: When coding, I understand what I need is: "When applied to a Range object, the property is relative to the Range object. For example, if the selection is cell C3, Selection.Range("B1") returns cell D3 because it's relative to the Range object returned by the Selection property. On the other hand, the code ActiveSheet.Range("B1") always returns cell B1."

However, to get TREND to do this without learning a lot more with the spreadsheet is unknown. If not available, then my suggestion is to have an option that allows this for the TREND function. I have used Excel for years without need for this for a lifetime, with TREND I have to modify the code every time I insert new data. While I have created a macro to do the expansion, copy and paste formulas, and rewrite the TREND command. It would be nice if a simple insert, and copy/paste worked, and the trend automatically followed.

If I knew that Excel formulas have a way to write this in the cell's code: I would learn it enough for this. However, not being sure; I can only write this suggestion.

It would be nice if inserting lines allowed the Trend to use data relative to it's new position, and not retain it's old position data, which is the previous week.

If it's easier to point me to a concept I'm missing about Excel; I would gladly accept a link to information to handle my issue; otherwise, a new ability would be desirable (either mine, or Excel's) lol

Thank you for your time!

Chip