You can change it in the UIR editor, by double-clicking on the panel and setting its properties. If you mean at run-time, you shouldn't edit the UIR file at run-time, it's a resource file that really shouldn't be changed at run-time. If you want to save the state of the panel from run-time (size, values of indicators, etc) you can use SavePanelState and RestorePanelState. You could also use an INI file where you are saving off the panel size and using SetPanelSize when you load the program that you read from the INI file.
Chris