c# - Route mouse-event to underlying control -

i have usercontrol grid whith 1 row , 1 column. column add combobox fills whole space of column. want put canvas-element on combobox in left corner. until here works fine.

the code:

<grid> <combobox style="{staticresource flat}" selectionchanged="colorselectionchanged" borderthickness="0" itemssource="{binding itemcol, updatesourcetrigger}"\> <canvas margin="5,5,0,5" width="25"  horizontalalignment="left" background="{binding selectedcolor, updatesourcetrigger=propertychanged}"/> </grid> 

if move mouse on conrtrol selection of combobox if i'm not on canvas. how can route mouse-events canvas combobox?

if canvas show, can turn off hit testing ishittestvisible="false" on canvas

http://msdn.microsoft.com/en-us/library/system.windows.uielement.ishittestvisible.aspx