I had to do something similar for my users, with a small variant that they want to have a running number grouping the similar items. Thought I'd share it here.
- Make a new column A
- Assuming the first row of data is in row 2 (row 1 being header), put
1
in A2
- Assuming your File No is in column B, in the second row (in this case A3) make the formula
=IF(B3=B2,A2,A2+1)
- Fill/copy-paste cell A3 down the column to the last row (be careful not to copy A2 by accident; that will populate all cells with 1)
- Select the data range
- In the Home ribbon select Conditional Formatting -> New Rule
- Choose Use a formula to determine which cells to format
- In the formula cell, put
=MOD($A1, 2)=1
as the formula
- Click Format, select the Fill tab
- Select the Background Color you want, then click OK
- Click OK
