Concat Columns

I found a small routine on msn that combines two olumns in a third. It works well.

Here it is.

Sub ConcatColumns()

Do While ActiveCell "" 'Loops until the active cell is blank.

'The "&" must have a space on both sides or it will be
'treated as a variable type of long integer.

ActiveCell.Offset(0, 1).FormulaR1C1 = _
ActiveCell.Offset(0, -1) & " " & ActiveCell.Offset(0, 0)

ActiveCell.Offset(1, 0).Select
Loop

End Sub

Here is my question. I need to alter this routine so that the macro will start at A1 and move to right until it finds its first empty cell and the combine all the strings of the cells it moved past.