Private Declare Function tapiRequestMakeCall Lib "TAPI32.DLL" (ByVal Dest As String, ByVal AppName As String, ByVal CalledParty As String, ByVal Comment As String) As Long

Private Sub PhoneCall(sNumber As String, sName As String)
    Dim lRetVal As Long
    lRetVal = tapiRequestMakeCall(Trim$(sNumber), Application.Name, Trim$(sName), "")
    If lRetVal <>  0  Then
        MsgBox "error"
        'Couldn't make the call.
        'Take appropriate action
    End If
End Sub

Private Sub Worksheet_BeforeDoubleClick(ByVal Target As Range, Cancel As Boolean)
Cancel = True
temp = ActiveCell.Value
    PhoneCall CStr(temp), "Calling"
End Sub