What would be the best formula to use in cell D4 that could be dragged to the other cells in the column, D5 and D6?

Without knowing the specific content of your spreadsheet, it's difficult to provide an exact formula. However, I can give you a general idea of how you might structure a formula that can be dragged down a column.

Let's assume that column D is meant to be a calculation based on the values in columns B and C. For example, if column B contains quantities and column C contains prices, and you want column D to show the total cost for each item.

In this case, the formula in cell D4 would be =B4*C4. This formula multiplies the value in cell B4 by the value in cell C4.

After entering this formula in cell D4, you can click on the lower right corner of the cell (where you see a small square, known as the fill handle) and drag it down to cells D5 and D6. Excel will automatically adjust the formula for each row, changing it to =B5*C5 and =B6*C6 respectively.

This way, the formula in each cell in column D will calculate the total cost based on the quantity and price in the same row.