think I found a solution...

public class SOMENEWMACROPARAM: DropDownList, IMacroGuiRendering
    {
        string _value = "";

        protected override void OnLoad(EventArgs e)
        {

            base.OnLoad(e);
// your custom dropdown list population here...
                    try
                    {//set the previous value
                        this.Items.FindByValue(_value.ToString()).Selected = true;
                    }
                    catch { }

                catch { }
            }
        }

        #region IMacroGuiRendering Members

        public bool ShowCaption
        {
            get { return true; }
        }

        public string Value
        {
            get
            {
                return this.SelectedValue;
            }
            set
            {
                this._value = value;
            }
        }

        #endregion

Seems to be working for me... :-)

Thanks for the solution!

is working on a reply...