I can't find this feature defined/explained anywhere, but I admit I'm having
a hard time knowing what search-phrase to use. Automatic Fill? Automatic
Input? Inputing Default Formula(s/e)? Anyway, here's the description of the
feature I need help with:

In some circumstances, when I type input into a column in a new row, Excel
will, in another column, autmatically place the formula that this other
column uses in other rows.

In sometimes the same circumstances, Excel doesn't do this, forcing me,
whenever I add/create a new row, to go to each column that has a default
formula and bring down that formula from previous rows using the manual
facilites (i.e. fill-down/copy/manual-input/etc.)

Specifically, I have a column where I provide the date. For sorting and
filtering reasons, I want to have a separate column for the weekday for that
date, so instead of formating the date-cell to include the weekday, I put the
formula: =TEXT(F2,"ddd") in the next column to the right (the G-Column). If
I go to the bottom of the spreadsheet and type the date into an F-Column cell
of a new row, Excel automatically adds the fomula =TEXT(F2,"ddd") into the
G-Column cell of the same new row. (If I choose "InsertRow" and add the
date, however, Excel does not autmatically input the formula.)

I cannot seem to re-create/control this facility with any other
formula/row/column/cell.

Does this feature have a name that I could use to look-up in Help? Is it
controlled by some "Option[Choice]" protocol? Is it triggered by how the
row/column-formula was created? Is it triggered by layout, such as one
column's adjacency to another? Or are there some functions (e.g. TIME
functions vs. FINANCIAL functions) that have this feature?

Anything anyone can tell me about this feature would help, because it would
be great to have more than one column automatically assume a formula of my
choosing every time I add a row.

Thanks!