In the On Success event of form "frmPlayer" I am trying to set the value for the picklist "Introducing_Player" (single-select dropdown field) for another record of the same form.

if (input.Name_before_edit  !=  input.Name)
{
    for each player in frmPlayer  [Introducing_Player == input.Name_before_edit]
    {
        player.Introducing_Player = input.Name;
    }
}

But this only works, if the value to be set (input.Name) already was a possible selection for this field before.

using the following code to extend the list of possible values is not allowed:

player.Introducing_Player:ui.add(input.Name);

What to do?