To be able to run a VBA macro that contains COMSOL API commands, you need to activate the reference to the ComsolCom DLL for the VBA project in the workbook. To do this, start by clicking the Visual Basic button on the Developer tab in Excel. In the Microsoft Visual Basic for Applications window that opens, go to the Tools menu and click References. In the Available References list select ComsolCom 6.4 and click OK.