If PS_PARAM has always 3 signs and the second one is always ";", try to ask your database in this way:
SELECT SUBSTRING([PS_PARAM],1,1) AS PS_VALUES
FROM [ERK].[dbo].[SM_POS_SETUP]
WHERE PS_CODE = 'A'
UNION ALL
SELECT SUBSTRING([PS_PARAM],3,1) AS PS_VALUES
FROM [ERK].[dbo].[SM_POS_SETUP]
WHERE PS_CODE = 'A'
which SUBSTRING() function returns part of string.
You should see results (2 rows):
Y
N
I have never used control: Janus.Windows.GridEX, so i can't help you more.
I think, you should load this data to datatable (not dataset) and populate it with column, but first you should change this part of code:
Column.EditType = Janus.Windows.GridEX.EditType.Combo
valueList.PopulateValueList(ds.Tables("PS_PARAM").DefaultView, "PS_PARAM")