Excel focus rectangle extension

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C++

Hi,

I'm new to Ultimate Grid (and relatively new to MFC). I have compiled the libraries and have a basic grid project up and running.

I have set it to display Excel-like focus and now want to be able to select a group of cells (say 3 in a column) and then extend the selection to copy the pattern established by the selected cells in a similar way to Excel continues the pattern.
Eg. I select 3 cells in a column, containing 1, 2, 3 respectively. If I extend the selection by 2 cells down I want to populate those cells with 1, 2. If I extend by 4 I want to populate them with 1, 2, 3, 1. I want to repeat the data, not extend the pattern as Excel does.

My problem is that I can't find any (obvious) methods which would allow me to detect when the mouse is over the small square in the bottom-right corner of the Excel Focus Rectangle so that I can change the cursor to indicate that, and to allow clicking the mouse to pick up that corner and extend the Focus Rectangle.

I have seen the Excel Demo and it doesn't seem to be able to allow the user to extend the Excel Focus Rectangle either, so I haven't been able to get clues from that.

Any help greatly appreciated.

Geoff King