Heath Thanks again. Your comments are sufficient for me to sort this out now. benny

Thanks Heath, Had totally missed the ref bit. Changed the declaration to what you suggested and then there were compile errors on the SetSystemTime call. Changed it to ” result = SetSystemTime(ref timeStru);” and also changed the result from int to bool. It works now. The reason for P/Invoke being public was that I cut and pasted it from a forum. My technique in building applications is to write and test little functions separately before moulding them into the final source. So these little stubs are often a bit sloppy. Thanks again benny

Thanks Can't use true as i get a compiler error: D:\Development\C++\Source\CheckBoxes\CheckBoxesDlg.cpp(195) : warning C4805: '==' : unsafe mix of type 'struct tagVARIANT (__thiscall CMdcToggleButton::*)(void)' and type 'const bool' in operation When using the class wizard to add a member variable the only choice i have is a category of control and a variable type of CMdcToggleButton. There are no other choices. If i use the standard checkBox then i get the categories of control and of value and the value bit works. As far as the updatedata, Here is the actual code: void CCheckBoxesDlg::OnClickToggleButton1() { UpdateData(TRUE); m_ToggleButton1Control.UpdateData(TRUE); m_ToggleButton1Control.GetValue(); if (m_ToggleButton1Control.GetValue == false) {m_ToggleButton1Control.SetForeColor(olive_note);} else {m_ToggleButton1Control.SetForeColor(red_note);} } As you can see i even did the update two different ways as an experiment. A similar function for a simple checkbox works perfectly: void CCheckBoxesDlg::OnClickFormsCheckBox1() { UpdateData(TRUE); if (m_FormsCheckBox1Control.GetValue == 0) { m_CommandButtonControl.SetForeColor(blue_note); m_CommandButtonControl.SetCaption("FormsCheckBox set on"); m_FormsCheckBox1Control.SetBackColor(blue_note); } else { m_CommandButtonControl.SetForeColor(yellow_note); m_CommandButtonControl.SetCaption("FormsCheckBox set off"); m_FormsCheckBox1Control.SetBackColor(yellow_note); } } Again thanks for any help as i'm baffled. benny