[Erel]

You can send the 'click' message to the control with Hardware.SendMessageToControl:
Pressing Button1 will show the calendar or hide it if it is already opened.

Sub Globals
    'Declare the global variables here.

End Sub

Sub App_Start
    Form1.Show
    hardware.New1 'Hardware object
End Sub

Sub Button1_Click
    hardware.SendMessageToControl("Calendar1",513,0,0) 'Change Calendar1 to your calendar name.
    hardware.SendMessageToControl("Calendar1",514,0,0) 'Change Calendar1 to your calendar name.
End Sub