apiary.AddPlus(THISBACK1(NewApiary, &apiary));
apiary.WhenAction = THISBACK(OnChangeApiary);

// Later in code, I populate it:
apiary.Clear();
apiary.Add(0, "All");
	
SQL & Select(ID.Of(APIARY), NAME.Of(APIARY))
    .From(APIARY)
    .OrderBy(NAME.Of(APIARY));

    while(SQL.Fetch())
        apiary.Add(SQL[0], SQL[1]);

// Later in code:

void BeekPRO::OnChangeApiary()
{
	LoadHives(apiary.GetData());
}

void BeekPRO::LoadHives(Value apiaryId)
{
    hives.Clear();
	
    if (apiaryId == 0)
        SQL & Select(ID, APIARY_ID, NAME, HIVE_TYPE_ID)
            .From(HIVE)
            .OrderBy(NAME);
    else
        SQL & Select(ID, APIARY_ID, NAME, HIVE_TYPE_ID)
            .From(HIVE)
            .Where(APIARY_ID == apiaryId)
            .OrderBy(NAME);
	
    while(SQL.Fetch())
        hives.Add(SQL);
}