In Cell B1 type in the following formula:
then drag this formula all the way across the columns in row 1 (as far as you want)
In Cell A2 type in the following formula:
then drag this formula all the way down the rows in Column A (as far as you want)
In Cell B2 type in the following formula:
here you'll drag this formula across and down the internals of the grid. how much will depend on what you did in the above two steps.
Cell A1 is going to be the place where you type in a number to determine the grid size.
You can also play with the column and row widths to get that 'grid effect'. Try also playing around with text alignment formatting and adding some background coloring.
Considering putting on some Sheet Protection (leave Cell A1 as unprotected) as to not accidentally mess up the formulas when changing the grid size.