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Well you are right that Flatten Variant doesn't work. I was mislead by a quick trial and had no time to verify further as I had to leave for private obligations. However I can't accept defeat so I remembered another post where someone wanted to have an VT_NULL Variant and investigating into the solution I have come up then showed an easy and totally official way to do it. The VARIANT memory layout is fully documented on MSDN and the LabVIEW Call Library Node supports explicitly the ActiveX Variant type. So simply passing the Variant as ActiveX Variant pointer to a C function that looks at the first two bytes in the structure is all that is needed to get at the VT_ values. Enclosed are the VI to create specifically a VT_NULL variant and the VI to read the VT_ type. I haven't entered the entire range of VT codes into the enum and since those codes are in fact not continous it is probably better to use a Ring control instead but that is an exercise left for whomever is wanting to use this VI. Get OLE Variant Type.vi NULL Variant.vi