Pulling dimension from a part in SolidWorks Macro

Hi Everyone, I am very new at VB and with macro in SolidWorks. As I have stated in the title, I am trying to find a way to pull the radius of the bottle base that is in contact with the ground/bottom plane and populated it in the user form or have it assigned to a variable so I can use it in calculation.

User Form V1.PNG shows the user form that I will be using to collect necessary data from the user. Currently, the user will have to manually measure the radius of the bottle in SolidWorks and input it in the userform. However, I would like to make it so that the user will not have to measure the radius, instead have the macro pull that data on its own and assign it to a variable so I can use it for calculation. I am really not sure, how to implement this or if there's a better method to go about this.

I apologize for the long writing but I wanted to make sure everyone understand what I am trying to get the macro to do. Thank you in advance. I really appreciate it.

SolidworksApi/macros