The file simultaneous.zip has been modified to allow access to a Fortran simultaneous equation routine, compiled as a dll.  The original file was posted in solving simultaneous equations.  The advantages of a compiled routine include:

• Much better performance
• Greater precision through use of Fortran 80 bit variables
• Better security

Performance for solving a set of simultaneous equations with 250 unknowns 10 times is shown in the screen shot below.  The Fortran dll is over 18 times faster than the VBA routine.

Fortran Gaussian Elimination routine

To install GES() either:
Create a Folder “Spread” under Windows\System32
Copy the file GE5.dll to the new Spread folder
or:
Copy the file GE5.dll to the Windows\System32 folder
Open the Visual Basic Editor and change:
Declare Function GE Lib “..\Spread\GE5.dll”
to:
Declare Function GE Lib “GE5.dll”

The download zip file includes spreadsheet Simultaneous.xls, the dll file GE5.dll, and the Fortran source code GE5.f95

The Fortran routine is based on a program published by CR Bond