You are allowed to pass arguments into any fixture.

Arguments are in cells that are to the right of the cell with the fixture name. The protected field args in Fixture holds a String array with the arguments.

Below you can see a simple RowFixture that takes a single integer argument and produces the prime factors of that argument.

fitnesse.fixtures.PrimeFactorsFixture	6
factor
2
3

The code for this fixture is shown below. Note that the query method uses the args field.
(Note the "6" that follows the fixture name above.) You can put as many arguments there as you like.

public class PrimeFactorsFixture extends RowFixture
{
  public static class Factor
  {
    public Factor(int factor)
    {
      this.factor = factor;
    }

    public int factor;
  }

  public Object[] query()
  {
    int n = Integer.parseInt(args[0]);
    ArrayList factors = new ArrayList();
    for(int f = 2; n > 1; f++)
      for(; n % f == 0; n /= f)
        factors.add(new Factor(f));
    return (Factor[]) factors.toArray(new Factor[0]);
  }

  public Class getTargetClass()             // get expected type of row
  {
    return Factor.class;
  }
}

Because this is a RowFixture, the order of the rows is unimportant. As shown below the rows will be matched and found regardless of their order.

fitnesse.fixtures.PrimeFactorsFixture	1000
factor
2
5
2
5
5
2

And of course any cells that are missing, or extra will be marked in red.

fitnesse.fixtures.PrimeFactorsFixture	63
factor
7
3
5