Access common (part program) variable using API

Question

Hardware: Okuma OSP-P200L
API Version: 1.15.0.0
How can I read and write the values of common variables?
I found the example code in the help file, but it doesn't explain how to set the current sub system. Also I am confused about the difference between AddCommonVariableValue() and SetCommonVariableValue() Could someone please give a clear example / explanation?

===GET===
Me.varValue.Text = objVariables.GetCommonVariableValue(CInt(Me.varCommonVarNumber.Text))

===SET===
objVariables.SetCommonVariableValue(CInt(Me.varCommonVarNumber.Text), Dbl(Me.varValueUpdate.Text))

Answer 1

Example (VB.NET):

Private Sub UpdateCommonVariable(ByVal iIndex As Integer, _
                                 ByVal enSubSystem As Okuma.CLDATAPI.Enumerations.SubSystemEnum)
    Try

        ' Assumptions:  iIndex = 1
        ' Current Value of Common Variable 1 is 0
        ' enSubSystem = Okuma.CLDATAPI.Enumerations.SubSystemEnu.NC_AL, 
        '    which is Left Spindle, A-Turret

        ' return Type from a Common Variable is always a Double
        Dim _dCommonVariableValue As Double

        ' declare 
        Dim _cVariables As New Okuma.CLDATAPI.DataAPI.CVariables


        '------------------------------------------------------------------------
        ' this sets the current SubSystem on the cVariable object
        _cVariables.SetSubSystem(enSubSystem)
        ' and this gets the value currently held by the Common Variable at the 
        ' speicified Index, in the specified SubSystem
        _dCommonVariableValue = _cVariables.GetCommonVariableValue(iIndex)
        ' the return is a Double, with value of 0
        '------------------------------------------------------------------------


        '------------------------------------------------------------------------
        ' these add a specified value to the value already held by the specified 
        '    Common Variable
        _cVariables.AddCommonVariableValue(iIndex, 1.5)
        ' the value at Common Variable 1 += 1.5, or = 1.5
        Dim _addValue As Double = 0.001
        _cVariables.AddCommonVariableValue(iIndex, 0.001)
        ' the value at Common Variable 1 += .001, or = 1.501
        '------------------------------------------------------------------------


        '------------------------------------------------------------------------
        ' SetCommonVariableValue
        _cVariables.SetCommonVariableValue(iIndex, 1.0)
        ' the value at Common Variable 1 is set to 1.0, overriding all 
        '     previous edits 
        Dim _setValue As Double = 12345.001
        _cVariables.SetCommonVariableValue(iIndex, _setValue)
        ' the value at Common Variable 1 is set to 12345.001, overriding all
        '     previous edits
        '------------------------------------------------------------------------


    Catch ex As Exception
        Throw
    End Try
End Sub