To answer your question specifically:

In short: Yes. The trick is for the form to know whether it is signing
someone in, or out. Having a method of knowing whether the sign-out time has
been entered or not that is as simple as possible would help. Using your
datastructure, here is what I would recommend.

First, instead of using "Date" and "Time In" and "Time Out" - I'd recommend
you kill the "Date" field and just use Time In and Time Out as "date" types
using the now() function. This will let you do math more easily in the
future, and will allow for easier error catching when someone scans in, but
forget to scan out. Or scans out twice etc. I'll write the following assuming
you've done that.

All your form needs is a Text Box with the "OnKeyPress" event activated.
Here is a sample of the Event. (Note: make certain you don't have a default
value for TimeOut. The Field must remain null after a Sign-In Entry for this
to work.)

Private Sub MemberID_KeyPress(KeyAscii As Integer)
Dim rst As Recordset    '   This will be the Recordset of your table, or
your row.
Dim ID As String        '   This will hold the Members ID
Dim Q As String         '   This is a String to hold a small Query

'   Define the ID
ID = Me.memberID.Value
'   Determine if there is a row where the "TimeOut" has not been entered.
Q = "SELECT * FROM [TABLENAME] WHERE memberID='" & ID & "' AND
isnull(TimeOut)=true;"
Set rst = CurrentDb.OpenRecordset(Q)    '   Opens a Recordset from Q

If IsNull(rst.RecordCount) = True Then '   If there is no record
   rst.Close                           '   Close the Recordset
   Set rst = CurrentDb.OpenRecordset("[TABLENAME]")    '   Open the whole
Table
   With rst                        '   In that table
       .AddNew                     '   Add a new Row
       .Fields("MemberId") = ID    '   Set MemberId
       .Fields("TimeIn") = Now()   '   Set Date/Time of Entry
       .Update                     '   Update the Record
   End With
   rst.Close                       '   Close the Recordset
Else
   With rst                        '   With the single-Row Recordset
       .Edit                       '   Edit this Row
       .Fields("TimeOut") = Now()  '   Set Date/Time of Exit
       .Update                     '   Update the Record
   End With
   rst.Close                       '   Close the Recordset
End If
End Sub

Hope this Helps!

Theo Geer