qgridlayout setting in qt designer

In qt designer, how to make qgridlayout so that it can contains
1 widget in first row, streched and 2 widgets in second row.

something like this:

Code:

---

-------------------------------- 
      widget1              
 
--------------------------------
  widget2   | widget3  
--------------------------------

---

tnx

Stretch the first widget to span 2 columns. Insert the no 1 and 2 widgets in the same column and the 3 in another. Than Drag the left edge of the no 1 widget so that it spans 2 columns.