Hello Uwe,
here are links to one tutorial and several examples for calling LabVIEW DLLs in LabWindows/CVI:
Creating and Calling LabVIEW DLLs with Various Data Types from CVI:
http://zone.ni.com/devzone/cda/tut/p/id/3187
Using LabWindows/CVI to Call LabVIEW DLLs That Pass Booleans:
http://sine.ni.com/devzone/cda/epd/p/id/4046
Using LabWindows/CVI to Call LabVIEW DLLs That Pass Clusters:
http://sine.ni.com/devzone/cda/epd/p/id/4923
Making a LabVIEW VI an Embedded Child Window of a LabWindows/CVI Panel:
http://sine.ni.com/devzone/cda/epd/p/id/4345
Transferring an ActiveX Reference Pointer to a CVI DLL:
http://sine.ni.com/devzone/cda/epd/p/id/3343
Best Regards
Plamen
National Instruments Germany
Application Engineer