If you want just the total number of records displayed in a text box then use the DCount function.
=DCount("*", "YourTableName") Check the help files for more info on using DCount.
If you want to display the record X of Y info in a label then try this...
Private Sub Form_Current()
If Me.NewRecord Then
Me.lRecordXofY.Caption = "New Record (" & DCount("*", "TableA") & " existing records)"
Else
Me!lRecordXofY.Caption = "Record " & [CurrentRecord] & " of " & DCount("*", "TableA")
End If
End Sub
The above is using a label named "lRecordXofY" and a table named "TableA".