$Title Portfolio Optimization in Excel $Ontext In this example GAMS runs only in the background. We use the vba version of the GDX API to write a GDX file from data defined in the spreadsheet. To solve the model we call the GAMS executable with a CreateProcess call out of vba. $Offtext $callTool win32.msappavail Excel $if errorlevel 1 $abort.noError "No Excel available" $call "start portfolio.xlsm"