The information here is applicable to the DLLs supplied with CLW6I23DAL.
A support file for 64-bit Visual Basic .NET (VB.NET), called clvbdnet64.vb, may be found in this zip file. This file can be used in 64-bit VB.NET code. Separate VBA7 headers are available for use with 64-bit Excel Visual Basic for Applications.
The file clvbdnet64.vb contains the VB declaration of each user-callable NAG C Library function and all Enum and Structure (Type) declarations necessary for the parameters (mandatory and optional). This file can be imported into your VB project.
The header file is based on the stand-alone version of the NAG C Library DLL (CLW6I23DA_nag.dll); to specify the version of the DLL which uses the MKL BLAS/LAPACK instead (CLW6I23DA_mkl.dll), replace CLW6I23DA_nag.dll by CLW6I23DA_mkl.dll in the Function and Sub declarations.
See the pages on using the NAG C DLLs from Visual Basic .NET (64-bit) for information on how to use these headers.