I have just uploaded a new version ULS Design Functions-biax, which can be downloaded (together with the uni-axial version) from:

ULS Design Functions.zip

The main changes are added code parameters from Eurocode 2:

Detailed output for a specified load and neutral axis angle is as in previous versions:

There are also functions that will generate various interaction diagrams:

For more details and examples see: Biaxial Bending Update.