Finding the last used row of a column, using this value to place text down another column

Hi I have been going round in circles with this one can anyone help?
In column A I have a certain number of values (this can vary ). Lets say Column A has data down to row 22. I would like "N/A" to be placed in the column B and H starting from B2 and H2: to the end of the range located in A, in this case 22.

I can find the end of column A with vba but I can not figure out how to autofill down column B and H with "N/A".

I have attached a spreadsheet just to make it bit more clearer. (I am using excel 2007)

Thanks for looking