Phil Chan writes to say
QUOTE:
I have downloaded several excel file from your web which is directly copy from the Roark's handbook. I don't know if there are built in function in excel so that we can directly input the x, y and z in he cell and get the result based on the provided formula.
They are just normal excel formulas - XLC just displays them as equations. If there is no equation shown next to a cell then it is likely to be an input cell. Change this value and the calculation will update just like a regular spreadsheet.