Here is the VBA call to my DLL. Fairly straight forward.

' compress to two outlet streams, vapor and liquid (if any)
CalculateIsentropicCompresssor Nin, Nout2, Ncomp, padtodouble, _
InletStreamTemperature(0), InletStreamPressure(0), _
InletStreamMolarFlowrate(0), _
InletStreamMolarFlowrateByComponent(0), _
OutletStreamVaporFraction(0), _
OutletStreamTemperature(0), OutletStreamPressure(0), _
OutletStreamEnthalpy(0), OutletStreamEntropy(0), _
OutletStreamMolarFlowrate(0), _
OutletStreamMolarFlowrateByComponent(0), _
WorkAvailable, IsentropicEfficiency, PressureOutSpec, _
CalculatedElectricalKwUsed, CalculatedWorkUsed, _
CalculatedIsentropicHead

I retyped this entire DLL call from VBA and it started working. Weird.

Lynn