Use Conditional Formatting.

Select your range of cells to apply the formatting to.
Click on "Conditional Formatting" (Home Tab, Styles Section)
Select "New Rule"
Select "Use a formula to determine which cells to format"
Enter the formula: =MOD(ROW(),2)=1
Click the "Format" Button
Select your format (blue fill)
Click OK

HTH,
Elkar


"Mikushg" wrote:

I am using excel 2007 and am trying to select a rather large spreadsheet and
have excell fill each alternating cell with a certain colour. ex. a1 blue
fill, a2 no fill, a3 blue fill, etc. etc.

Please help