qd.Connect =  ";DATABASE=X:\y\z.mdb;UID=admin;PWD=" 

    Dim db As Database, qd As QueryDef, sQueryName As String, sConnect As String
    sQueryName =  "Test_Q" 
 -->   sConnect = ";DATABASE=X:\y\z.mdb"
 
    DefPassTroughQuery db, qd, sQueryName, sConnect

Function DefPassTroughQuery(db As Database, qd As QueryDef, sQueryName As String, sConnect As String)
    Dim i As Integer
    Set db = CurrentDb()
    For i =  0  To db.QueryDefs.Count -  1 
        If db.QueryDefs(i).name = sQueryName Then
            db.QueryDefs.Delete sQueryName
            Exit For
        End If
    Next i
    Set qd = db.CreateQueryDef(sQueryName,  "select * from T" )
 -->    qd.Connect = sConnect
 
    qd.ReturnsRecords = True
End Function