Replacing Access 2010’s TAPI AutoDialer with a No-Frills Dialer using the Hayes ATDT Command

Background

Adding an AutoDialer button with the Command Button Wizard creates an embedded macro that runs Windows’ built-in Dialer.exe, a Telephone API (TAPI) application that reads configuration data and dialing rules from Control Panel’s Phone and Modem tool. By default, the macro transfers the phone number from the preceding control in the tab order to a text box. Clicking the button opens a dialog that lets the user confirm (and, optionally, edit the number), and then click OK to dial or Cancel to abort it:

Clicking OK also activates an AutoDialer icon in the taskbar:

Clicking the taskbar icon opens the following two dialogs anchored ot the top left of the screen:

Most developers and their clients will consider these two dialogs superfluous and confusing to end users. What’s worse, there appears to be no readily apparent method for preventing the Phone Dialer dialog from appearing when the user just wants to hang up. Users expect to “hang up” simply by placing the handset on hook.

Extensive searching with Bing and Google disclosed no free, turnkey code for creating a simple autodialer by executing the Hayes ,,ATDT+1###-###-####;H command to dial the number and hang up.

Creating the No-Frills Dialer with David M. Hitchner's modCOMM Library

Access 2010’s VBA 7 doesn’t have a feature that emulates VB 6’s MSComm control, but David M. Hitchner has thoughtfully posted a VB module containing a collection of routines to perform serial port I/O without using the Microsoft Comm Control component here. His CommIO.zip file contains a CommIO.bas and SampleCode.txt files. Rename CommIO.bas to CommIO.txt, open it in Notepad and paste it into a new module.

Important: Be sure to add PtrSafe to CommIO’s Declare statement if you’re running 64-bit Access or either 32-bit or 64-bit Access under Windows 8 or Server 2012, as in:

Declare PtrSafe Function GetCommModemStatus Lib "kernel32" _
    (ByVal hFile As Long, lpModemStat As Long) As Long

Here’s my code for a procedure that accepts arguments for the form name, control name of the text box with the phone number, and name of the dialed party, opens this message box:

and sends the COM port number (2) and ATDT command text to a subprocedure based on David’s SampleCode.txt example:

Public Sub AutoDial(strForm As String, strControl As String, strParty As String)
    ' Dial with Hayes-compatible command set
    On Error GoTo ErrorHandler
    Dim Phone As Control
    Dim Party As Control
    Dim strNumber As String
    Dim strDialCmd As String
    Dim strMsg As String
    Dim varRetVal As Variant
    Set Phone = Forms(strForm).Controls(strControl)
    Set Party = Forms(strForm).Controls(strParty)
    varRetVal = Application.SysCmd(acSysCmdClearStatus)
    If Len(Phone.Value) = 12 Then
        If Left(Phone.Value, 3) = "510" Then
            ' Local call
            strNumber = Mid(Phone.Value, 5)
        Else
            ' 1-AAA-PPP-NNN
            strNumber = "1-" & Phone.Value
        End If
        strMsg = "Click OK to dial " & strNumber
        If Len(Party.Value) > 0 Then
            strMsg = strMsg & " for " & Party.Value
        End If
        strMsg = strMsg & " and pick up handset within 10 seconds."
        strMsg = strMsg & vbCrLf & vbCrLf & "Or click Cancel to abort the call."
        
        strDialCmd = ",,ATDT" & strNumber & ";H"
        varRetVal = Application.SysCmd(acSysCmdSetStatus, "Dialing " & strDialCmd)
        If MsgBox(strMsg, vbOKCancel + vbQuestion, "Pacific Park Plaza Autodialer") = vbOK Then
            ModemDialer 2, strDialCmd & vbCrLf
        End If
    Else
        MsgBox "Phone number not valid.", vbOKOnly + vbExclamation, "Autodialer Error"
    End If
    Set Phone = Nothing
ExitPoint:
    Exit Sub
    
ErrorHandler:
   MsgBox Err.Description, vbExclamation, "Unexpected Autodialer Error"
   Resume ExitPoint
End Sub

You must specify the modem’s COM port to correspond with Control Panel’s Phone and Modem tool in the first argument of the above ModemDialer 2, strDialCmd & vbCrLf instruction:

Here’s the modified procedure for invoking CommIO functions:

Sub ModemDialer(intPortID As Integer, strData As String)
    ' Truncated version of David M. Hitchner's SampleCode.txt from modCOMM.zip
    ' Requires installation of David M. Hitchner's modCOMM library downloaded from
    ' http://www.thescarms.com/vbasic/CommIO.aspx
    On Error GoTo ErrorHandler
    ' intPortID = 1, 2, 3, 4 for COM1 - COM4
    ' strData = Phone number with area code removed for local numbers and
    ' +1 prepended for out-of-area numbers
    Dim lngStatus As Long
    Dim lngSize As Long
    Dim strError  As String
    Dim varRetVal As Variant
    ' Initialize Communications
    lngStatus = CommOpen(intPortID, "COM" & CStr(intPortID), _
        "baud=9600 parity=N data=8 stop=1")
    DoEvents
    
    ' Write data to serial port.
    lngSize = Len(strData)
    lngStatus = CommWrite(intPortID, strData)
    If lngStatus = lngSize Then
        varRetVal = Application.SysCmd(acSysCmdSetStatus, strData)
    Else
        varRetVal = Application.SysCmd(acSysCmdSetStatus, "Error: " & strData)
    End If
    DoEvents
    
    ' 10 seconds to pick up phone; see procedure below
    Pause 10
    varRetVal = Application.SysCmd(acSysCmdClearStatus)
    Call CommClose(intPortID)
    
ExitPoint:
    Exit Sub
ErrorHandler:
    MsgBox Err.Description, vbInformation + vbOKOnly, "Error Opening COM Port"
    Resume ExitPoint
End Sub

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