There are two ways to do this, one is call LoadGridRow or LoadGridCell, that will fire OnDefineButtons allowing you to call AddButton to specify the buttons you need. Of course then you need to make sure that inside OnDefineButtons you get the details you need (global buffers or make a property (does not need to be a web property) that you set inside OnManualLoadData. The LoadGridRow will return the entire row struct for you, the LoadGridCell only fills a single tWebCell struct.

The other is fill the the tWebCell struct yourself in which case you need to know what to put where. The format is that for each button you add three items to the aOptions array:
1. button ID (will be sent to onclick)
2. CSS Classname applied to this button
3. Caption of the button