I am not sure whether I can achieve this way of doing in Oracle Form 6i such as the subtotal function like excel ? Whereby from the data block it will have all rows of data in detail and if user click on a button/ radio check then it will change to summary column from the same datablock in the same canvas or layout.
You should be able to do this using a couple of Stacked Canvases. Create a Stacked Canvas and Data block to show your rows of data. Then create a second Stacked Canvas and a seperate data block that sumarizes your data they way you want it. Then use the code in your Button's When-Button-Pressed trigger to cycle through displaying/hiding the canvases. You can cycle between the canvases by looking at the GET_VIEW_PROPERTY('STACKED_CANVAS_NAME',VISIBLE) property. It returns 'TRUE' if the canvas is visible in any way and it returns 'FALSE' if it is not visible at all.