VBA - "Close"/UN_DropDown a combobox list?

I'm working on a dynamically filled Excel combobox, but sometimes when I update the list inside, the display gets crazy.

As I fill and check the list, I use these :

1. to adjust the number of visible lines

   If .ListCount > 14 Then
       .ListRows = 15
   Else
       .ListRows = .ListCount + 1
   End If
   

2. to display/unwrap the list (anyCB is an Object parameter in my Sub)

   anyCB.DropDown
   Set Cbo = corresWS.OLEObjects(anyCB.Name)
   Cbo.Verb xlVerbPrimary
   

But sometimes, there is still 15 visible lines but a litlle slider inside the big (15) one, to scroll through all the lines in a single one... :/

So I'm wondering if there is any way to close/unwrap/retract the list before changing the number of visible lines. On any other workaround that you could suggest ;)