Using Cells From Other Worksheets Inside a Formula
For larger or more complicated projects you may need to spread data across multiple worksheets within the same project. In that case, you can still make formulas that use data from various worksheets.
To accomplish that, you can start writing your formulas as usual, and then click the desired worksheet tab, and then select the cells from within that worksheet. This will insert the name of that worksheet followed by an exclamation mark, which tells excel to handle it as a worksheet name.
For instance, if using a monthly spreadsheet, you can use data from the October sheet by clicking the October tab while writing the formula. This will place the word "October!" before the cell address you need in the formula. For data from other months that you want in the same formula follow the same pattern. This will tell Excel which sheets to draw information from.
Using this simple trick, you can pull values and variables from every corner of an Excel project and deposit them into your formulas.