Column with formula to be edited when user selects "custom"

[guasi]

I'm new to AppSheets and this forum. I'm wondering if it's possible for the value of a column to be the result of a formula, which includes an option to be editable by the user.

I have a filterdate table, with three columns, Filter (enum), Start (Date), End (Date). Right now, upon selection of the Filter value (All Dates, This Month, This Year, Last Month, Last Year), a formula calculates the value for Start and End.

The formula for Start looks like this

IFS(
([Filter] = "All Dates"),  MIN(transactions[Date]),
([Filter] = "This Month"), EOMONTH(TODAY(), -1) + 1,
([Filter] = "This Year"),  DATE(CONCATENATE("01/01/",YEAR(TODAY()))),
([Filter] = "Last Month"), EOMONTH(TODAY(), -2) + 1,
([Filter] = "Last Year"),  DATE(CONCATENATE("01/01/",YEAR(TODAY())-1))
)

It all works fine, but I wanted to add an option "Custom" to allow the user enter Start and End date fields.

Is that possible? 

[TeeSee1]

Set the expression in the Initial Value of the column.

Users can change it if they want to.

[guasi]

Thank you for the suggestion. Setting the expression in the Initial Value of the column does not do what I want. When the user selects from the dropdown different options, the value of Start does not change. It seems the Initial Value is exactly that, only an initial value, not a value that changes upon changes on another column, which is what I want.

Other ideas?

[TeeSee1]

Initial value DOES change based on the value of other table(s) if you have the right expression.  See here.

[guasi]

Thank you for the link. The detailed explanation states why it won't work in my case. The Initial Value expression only works for the first time a record is created, not when the record is being edited. "An Initial value expression assigns an initial or default values for a column in a new entry. ... Its value will be recomputed as the new entry is filled in until the user explicitly sets the value of the column. At that point, a value has been assigned and the Initial value definition is no longer relevant for this entry."

What I have is a user setting that is only editable, there will never be a new record. 

Thanks for the clarification. I've found a work around. I'm adding the filter elsewhere.

[TeeSee1]

Glad you found a work around.

JFYI, there is also an option Reset on Edit that could have worked for you.