Hi,
As far as I could find out, if your developers implement the TVS_CHECKBOXES style, the mechanism that is used in your controls at the moment will stop working. So, they will have to modify the code anyway. Also, there are several reasons why your developers may not implement this style. The TVS_CHECKBOXES style lets draw the check boxes using standard functionality provided by the operating system. So, it includes only two states for a check box: checked or unchecked. Also, it doesn't allow changing the icons for the check boxes. So, your developers may not use this style, because they wanted to add more states or other icons for the check boxes (it's just my guess).
As a conclusion, your developers may agree to implement this style, but, I think, it's "a hundred to one" :)
