As tina said:

    msgbox dlookup ("[f2]", "[tbl]", "[f1]="""username""")

where f1 is the name of the first field, tbl is the name of the table,
and f2 is the name of the second field.

I don't understand what you mean. Dlookup will find the record with a
specified value for the first field & return the value from the second
field in that record. What else do you want to do? Where does a
recordset come in?

HTH,
TC

If I understand what you are trying to do, you want to check if the record
exist and if it doesn't add it to the table

Dim MyDB As DAO.DataBase, MyRec As Dao.RecordSet

Set MyDB=CurrentDB
Set MyRec = MyDB.OpenRecordSet("Select * From TableName Where
UsernameFieldName = '" Me.Username "'")
If MyRec.Eof Then
   ' Doesn't exist
   MyRec.AddNew
   MyRec!Username = Me.Username
   MyRec.Update
Else
   MsgBox "Username exist"
End If
===================================================
' I hope that will get you started, if the field you are looking for is
number type use that
Set MyRec = MyDB.OpenRecordSet("Select * From TableName Where
UsernameFieldName = " Me.Username)
==================================================
I assumed that you are looking for a field value in a form and this is why I
used Me.Username, if it is a different variable then use yours

DLookup([field1], [tableName], "[field2] = criteria")

if you're simply want to check for the existence of value in a table, so as
to take an action based on whether or not the value exists, a DLookup should
do it for you. it's easier, and shorter, to write than opening a recordset
and searching it; and AFAIK, there's little or no difference in speed.

perhaps you're trying to do this the hard way around. using a GoTo statement
in your code suggests that possibility, since there's rarely a real need to
use it outside of error handling. suggest you post the VBA code; maybe we
can suggest an easier way to accomplish your goal.

hth