Implement Show Formulas command, which display the formulas in the cells instead of the result value. In MS Excel, this is available in Formulas -> Formula Auditing -> Evaluate Formula.

The keyboard shortcut is "Ctrl + ~".

Implement AutoSum command and functionality. In MS Excel, it is located in Home -> Editing -> AutoSum drop down, and allows fast creation of formula over the selected cell, by choosing a formula: SUM, AVERAGE, COUNT, MAX, MIN, etc. If a range is not selected, the command tries to predict which sells have be included.

At this point, the formatting can be applied only to the whole cell content.