Does anyone have any suggestions on how to do it in excel?

When I combine 4 cells into a big cell, and type in the formula.
This formula requires to key in Ctrl+Shift+Enter to activate the formula
function.
I can key in Ctrl+Shift+Enter within a single cell, but I cannot do it in a
big cell, which is combined by a number of cells.
Does anyone have any suggestions on how to key in Ctrl+Shift+Enter into a
big cell?
Thanks in advance for any suggestions
Eric