make sure u know $ absolute and relative reference
In spreadsheet applications, a reference to a particular cell or group of cells that does not change, even if you change the shape or size of the spreadsheet, or copy the reference to another cell. For example, in Lotus 1-2-3 and other spreadsheet programs, the cell reference "$A$3" is an absolute cell reference that always points to the cell in the first column and third row. In contrast, the reference "A3" is a relative cell reference that initially points to the cell in the first column and third row, but may change if you copy the reference to another cell or change the shape and size of the spreadsheet in some other way. Absolute cell references are particularly useful for referencing constant values (i.e., values that never change).
In spreadsheet applications, a reference to a cell or group of cells by indicating how far away it is from some other cell. For example, in Lotus 1-2-3 and many other spreadsheet programs, the cell reference "C2" is relative. Initially it points to the cell in the third column and second row, but it does this by specifying how far away this cell is from some other cell. For example, if you insert this reference in cell A1, the program will translate it to "2 columns right and 1 row down". If you then copy the reference to cell B4, it will now point to cell D5.