Create a dependent drop down list

Is it possible to create two drop down list such that the 1st list will show the category and the second list will only show the account under the selected category in 1st list box ?
However, I don't want to name each category and account in a name range as the rows are always changing.


Category                    Account
--------------                  -------------  
O&M Costs      O&M Contract
O&M Costs      R&M Labour
O&M Costs      R&M Materials
Salaries & Benefits      Salaries
Salaries & Benefits      Bonuses
Salaries & Benefits      Pension Contribution
Salaries & Benefits      Health Insurance
Salaries & Benefits      Travel Insurance
Salaries & Benefits      Other Employee Benefits
Training, Development and Recruitment      Recruiter Fees
Training, Development and Recruitment      Job Advertising Fees
Training, Development and Recruitment      Other Recruitment Expenses
Training, Development and Recruitment      Training & Development