Softimage SDK Programmer's Guide > Customizing Softimage using the SDK > Custom Properties >

# Defining On-the-fly Property Pages

If you are defining your property page on the fly, you can use the same callbacks as for a self-installing property (with a slightly different naming convention), but you have to explicitly attach the Logic (the callbacks) to the property page. There are two ways to do that:

- You can use the PPGLayout.Logic property (which corresponds to the siUILogic layout attribute) to attach each callback function as one long string.

- You can use the siUILogicFile layout attribute to specify the path and filename of the script file where your Logic resides.

## Specifying the Language for the Logic Section

You can use the PPGLayout.Language property (which corresponds to the siUILanguage layout attribute) to set the language used for the implementation of the Logic section. The default scripting language is VBScript, but you can specify JScript and Python.