Lynn,
I'm thinking that if your UI calls the DLL then it runs in-process
rather than in its own space. If your UI is a C++ EXE then the same
methodology is being applied to handle the DLL's returned value.

As I stated in your previous post on 3/15, Excel/VBA handles double
precision in its own way and so the return from your DLL got grabbed up
in that process. As JoeU suggests, I suspect Excel is modifying the
return for use with VBA. I use VB6 or PowerBasic DLLs and have no FPU
discrepancies.

You might get more help if you ask this in "comp.lang.C++"...

--
Garry

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