Chr(39) is the single quote (').
You only need this if the MUFLID is of type text. If MUFLID is numeric, you should omit the chr(39)

BTW, you could have just typed the quotes.
"SELECT * FROM [tbl * F002 > 4 J] WHERE MUFLID = '" & ddlWho.SelectedItem.Text & "'"

Also make sure ddlWho.SelectedItem.Text doesn't contain single quotes!, if it does, you need to replace every single quote with two single quotes.