Delete Cell Numbers of Column B From Column A (Column B Small and Column A too big)

I am new to use Excel.I am using MS OFFICE PROFESSIONAL PLUS 2010.
Operating system Windows 7. I have 50 Lacs Local Cell Numbers and i want
to delete my competitors cell numbers from this big list which is 302 cell numbers.

I divide this big list into 5 Sheets because each excel sheet allow 1048576 rows.
The big list is paste in column A and the competitor list is paste on column B.

Column "A" have all cell numbers
Range = (A2:A1048576)

Column B have all competitors cell numbers
Range = (B2:B302)

Column C for refine result without competitors

I want to delete Column B values from column A so what can i do for it.

Hi
I think if you upload a sample file it will be a great help!!!!