problem with running a cst macro with matlab

Hi all

I have written a Matlab function to start a global macro 'single_ports' on a cst disign project. Basically it looks like this:

oCSTApp = actxserver('CSTStudio.Application');
oMWSProject = invoke(oCSTApp,'OpenFile',projectname);
invoke(oMWSProject,'RunMacro','single_ports');

Matlab throws that there's a internal error in CST right after invoking 'RunMacro'. But it's tough to examine since the macro will run pretty fine if I start it within CST.
Has anybody any idea?