VBA User Form - Option Button

Dear Friends,

I need some help regarding the option buttons created in VBA Userforms.

You can find the Spreadsheet attached here for reference regarding the issue.

I have created a form "frmSelection" and it pops up when the "Check Section" command button is clicked. After displaying the form, I tried to keep option button "IS800-1984" default enabled.

If user changes the "Code Selection", for example "IS 800-2007" then another form will be displayed, i.e., frmIS8002007.

When this form is opened, I want to keep "Simply Supported", "Restrained" and "Hot Rolled Sections" enabled by default.

I even wrote the corresponding code but I am unable to get these controls enabled by default.

Kindly refer to the attached sheet and suggest me.

Thanks in advance
Srinivas