The difficult I do immediately, the impossible takes a little bit longer.

Function frmValidateData() As Boolean
On Error GoTo ErrHandler
'For use with forms that have no subforms

     Dim ctl As Control
     Dim blnValid As Boolean
     Dim frm As Form

     Set frm = Screen.ActiveForm

   blnValid = True

   For Each ctl In frm.Controls
      If ctl.Tag <> "" Then
        If ctl.Enabled Then
          If InStr(1, ctl.Tag, "require") Then
            If Nz(ctl, "") = "" Then
              blnValid = False
              MsgBox (ctl.Name & " cannot be empty.")
              GoTo Complete
            End If
          End If
        End If
      End If
   Next ctl

  Set ctl = Nothing
  frmValidateData = blnValid
  Exit Function

  blnValid = False
  MsgBox ("Error validating: " & Err.Description)
  Resume Complete
  End Function

Place the below in your modUtilities or in a new Module, remembering not to name the Module the same as the Function, and save.  To use...
1.  On every control on your Form you want to be filled before saving or going to a new record place *require* (no asterisks) on Tag line in the Properties Window of said field(s).  To use...
If frmValidateData Then
     intResp = MsgBox("Your Question?", vbYesNo + vbQuestion, "Your Title?")
     If intResp = vbYes Then
        Call LogChange(Me.txtID, "frmYourForm", "Your Note of What Was Done.")
        strSQL = "UPDATE tblYourTable SET ytYourField = 5 WHERE rID = " & Me.txtID
        CurrentDb.Execute strSQL, dbFailOnError
     End If
        DoCmd.RunCommand acCmdSaveRecord
        Call SendeMail
        DoCmd.SelectObject acReport, "YourReport", True
        DoCmd.PrintOut , , , , 2
End If
The code will not execute if the ALL the fields tagged *require* are not filled in.  Instead you will get a message telling which fields are not filled in.