Task.WindowState (Word)

Returns or sets the state of the specified document window or task window. Possible return values are wdWindowStateMaximize - Maximized, wdWindowStateMinimize - Minimized, wdWindowStateNormal - Normal.

For Each myTask In Tasks 
 If InStr(myTask.Name, "Microsoft Excel") > 0 Then 
 myTask.Activate 
 myTask.WindowState = wdWindowStateMinimize 
 End If 
Next myTask