You can remove the auto-complete option in calc in LibreOffice by selecting from the Menu

Tools -> Cell Contents

and uncheck the AutoInput option provided.

In order to create a custom key shortcut in KDE (I am currently using 4.4.5) you should do the following:

1. Visit System Settings
2. Select Input Actions under Computer Administration
3. Right-click on Preset Actions and follow the path
   1. New
   2. Global Shortcut
   3. Command / Url

Having done so you should see something like