Hello,
try it in this way:
CString filename = L".......";
BRepBuilder builder;
TopoDS_Shape shape;
//Before using the filename convert it into Standard_CString by:
Standard_CString FileName = (Standard_CString)(LPCTSTR) filename;
BRepTools::Read(shape,FileName,builder);
There is a fine examples in the samples:
Look for samples\mfc\05_ImportExport ( in the case of OCC 6.5.0)
Regards