Spreadsheet Excel formulas

 To color alternate rows in Excel sheet:

1. Select the rows for which you need color fill.
2. Select Conditional Formatting and then New Rule to display the New Formatting Rule dialog box.
3. Select “Use a formula to determine which cells to format” as Rule Type:
   and type the formula "=MOD(ROW(),2)=0"  as shown in screen shot image below
4. Click button Format...  and select the Fill tab from Format Cells dialog box.

The settings can be changed later,  If you need to Edit existing rule then Select Conditional Formatting and then Manage Rules...  to displayConditional Formatting Rules Manager dialog box. 

Reference : http://www.hotexcel.com/2010/11/21/how-to-color-alternate-rows-in-a-ms-excel-2010-table/

Concatenate :
If the required text string in column 'C' is first 2 characters of Column 'A' and First 6 characters of Column 'B'

Then the formula to be used in Column 'C'  is =CONCATENATE(LEFT(A2,2),LEFT(B2,6))