Sure, I can help you with that. Here's a step-by-step guide on how to generate dates on a semi-monthly basis in Excel 2003:

1. Start by entering the first pay date in a cell, let's say cell A1. In your example, this would be 4/15/2008.
2. In the cell below it, enter the first semi-monthly pay date. In your example, this would be 4/30/2008. Let's say you enter this date in cell A2.
3. Now, select cells A1 and A2 and drag the fill handle (the small black square at the bottom right corner of the selection) down as far as you need to generate the dates. Excel will automatically fill in the dates on a semi-monthly basis.
4. If you want to make sure that the dates are always on the 15th and last day of the month, you can use the following formula in cell A2 instead of manually entering the first semi-monthly pay date:
   
   
   Formula:

   =DATE(YEAR(A1),MONTH(A1),IF(DAY(A1)<=15,15,IF(DAY(A1)<=31,31))) 

   This formula checks the day of the first pay date and returns the 15th or the last day of the month accordingly. You can then drag the formula down to generate the rest of the dates.
5. That's it! I hope this helps you generate semi-monthly pay dates in Excel 2003.