Do a web serch for TVichw32, it's a small DLL/VXD the you can compile easily
for CVI that does just that (I use v2.0).
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Guillaume Dargaud
CNR/IFA
http://sung3.ifsi.rm.cnr.it/~dargaud/
http://sung3.ifsi.rm.cnr.it/~domec/
http://sung3.ifsi.rm.cnr.it/~chooyu/
"The church is near, but the road is icy. The bar is far, but we will walk
carefully." - Russian Proverb.