Cells stay highlighted, cannot use mouse

[Guest]

When I click on a cell in excel, that cell shows as clicked on, but when I move the mouse all surrounding cells become highlighted as well. So I cannot input anything anywhere, as moving the mouse around just keeps highlighting cells. And I cannot shut excel down as trying to move the mouse to a menu bar keeps highlighting cells in the worksheet. The only way to get out of excel is to End Task. I have come across this problem before, but I don't know how I inadvertently activate it, and to stop it was some combined of Ctrl-Enter but I can't remember what. Hopefully someone will understand this and be able to assist me. Thank you!

 

[Frank Kabel]

Hi
you have probably invoked the 'extended selection'. Check if there is
an 'EXT' in the statusbar. To switch back hit the F8 key

 

[Guest]

Hi Frank,

No EXT showing, but I can see how to switch it on and off via F8 (thanks for that tip!). I have the same problem in any file I open or any new file. I have tried another mouse, and that does not seem to be the problem. The arrow keys etc no longer work when this happens. If I start to type in Cell 1A as soon as I open a file, I can do this, but as soon as I use the mouse it starts highlighting everything again. Any other ideas?

Lisa