dynamic range - sort

I am creating a button on top of column A which will provide Sort capability. Clicking on this button will allow me to sort the worksheet based on Column A. The problem is that the data is continously changing on this worksheet. Today there might be 10 columns but tommorrow, I might have 20 columns. In addition, as far as the rows goes - the data which should be sorted is up until the point it encounters a blank row. Is there a simple sort function that I can use to accomplish this?

Or, how can I check for a blank row? Secondly, How can I handle the dynamic range of columns?

Thanks much !