amadeu_j, I appologize, but I just tried this and this creates a "forward depenency" error message (I thought that I have done this in the past, again, sorry for misleading you).

The best solution is to alter your SQL, basically the same way you attempted to adjust the 2nd parameter. Something like:

WHERE columName BETWEEN @Parm1Date and DATE_ADD(year, -1, @Parm1Date)

since all your really need is to work off of one date.