CUDA dll (64bit) vs MS Excel (32bit)

Hi all,

I am working in a bank and we use Excel extensively to prepare data then trigger our own pricing dlls. These dlls are slow and we hope to accelerate using CUDA/GPU.
Our setup is: Win7 64bit / Win2008 R2 64bit, Excel 2007 (32bit). Now with CUDA 64bit installed.

Can ask which solution is possible, or preferred?

1, build 64bit CUDA dlls using our 64bit CUDA installation. Then install Excel 64bit & rebuild all other linked dlls to be 64bit
2, build 32bit CUDA dlls using our 64bit CUDA installation (whether possible?), then use with other 32bit dlls & Excel
3, build 32bit CUDA dlls with a new 32bit CUDA installation (possible in a 64bit Windows?), then use with other 32bit dlls & Excel

Thanks,
Gengpu