Hi Ben,
Sorry for the long delay in getting back to you.
In GGC we have an option called FormModeTemplate. This will get raised when you get into the the Edit mode. We can have the our own controls inside the Template. Once if you press the Save button, the values entered in the controls of the Template get stored in the Grid.
Please have a look at the sample from the below link, which illustartes the above:
C:\Documents and Settings\User Name\My Documents\Syncfusion\EssentialStudio\6.3.0.6\Web\grid.grouping.web\Samples\2.0\Editing\FormEditMode\cs
You can also refer the sample from online through the below link:
http://www2.syncfusion.com/samplebrowser/samples.aspxPlease let me know if this helps you out.
Regards,
Raji