set_CustomInfo didn't work

Hello,all,I got a question here,please help me.Here's my question.

There's a combobox in my custom property.It's name is combobox.It looks like this in my custom property edit page.

At first,the combobox's value is empty.After I used code to change it,it's value change to com1,the code works.The code is:

swDoc.set_CustomInfo("combobox", "com1");

The page looks like this:

Ater this,I used this code:

swDoc.set_CustomInfo("combobox", "com2");

I wanted change the combobox's value to com2,but it didn't works,the value still is com1,it didn't change to com2.

My quetions is the code of funciton swDoc.set_CustomInfo() works first time,from the second time it didn't work,I think it's the type of combobox affect it.

Anyone knows how to fix this?Thank you.

SolidworksApi macros