How to export field as .txt format from CST vith Matlab

Here are the code so far:
cst = actxserver('CSTStudio.application');
mws = invoke(cst, 'NewMWS');
app = invoke(mws, 'GetApplicationName');
ver = invoke(mws, 'GetApplicationVersion');
invoke(mws, 'OpenFile', 'G:\zhang1\rectangle.cst');
result=invoke(mws,'Result3D','E-Field\e(f=2.45)(1(1)));


I don't know how to modify this code:result=invoke(mws,'Result3D','E-Field\e(f=2.45)(1(1)));

Please help.