Substituting a value from another column

[AlexShevyakov]

Hi,

Was looking for a way to utilise data substitution, when a user selects data from one column but the App inputs data from another.

Say we have the following schema:

Two Sheets.
One for data to be fed to DropDown [ColumnB];
One where User inputs are stored [ColumnA].

User selects a value from a list, fed from Column B.
VALID_IF $DataSheet[ColumnB]

What I need is when Item Aaa is selected, the value 1 is recorded in the UserSheet[ColumnA].
Tried something like:
SELECT($DataSheet[ColumnС], $DataSheet[ColumnB] = UserSheet[ColumnA], TRUE)
however, not successful.
Would appreciate a hint on this.
Thank you,
Alex