I have a dropdown on the ribbon that contains the names of worksheets. I have worked out how to make it update to include new work sheets in the list as they are created, what I cannot work out how to do is change the width of the dropdown dynamically. I know how to set the width in the customUI.xml file (sizeString property). I want sizeString to be set on-the-fly to the width of the name of the worksheet with the longest name, so that it is small if all the worksheet names are short but longer to accommodate longer names. (I know about invalidating the ribbon to reflect dynamic changes, I just do not know the correct syntax to change the width of the dropdown, or even if this is possible).