How to get by default selected menu in a dynamic menu list.

Hi,

How to get by default selected menu in a dynamic menu list.

My codes are


var row = new Object();
row.linkDestination = mainMash;
row.parentMenuId = "Menu";
row.menuId = "Menu_0";
row.isDefault = true;                      // I make it true to get default selection but it's not working.
row.imageURL = "";
row.linkTarget = "Self";
row.description = "";
row.linkType = "Mashup";
row.title = "MAP";
result.AddRow(row);

row = new Object();
row.linkDestination = mainMash;
row.parentMenuId = "Menu";
row.menuId = "Menu_0";
row.isDefault = false;                   
row.imageURL = "";
row.linkTarget = "Self";
row.description = "";
row.linkType = "Mashup";
row.title = "REPORT";
result.AddRow(row);

Is it correct? Please help me with that. Thank you!