Add record with related multiple records

I have a form Blogs which has a multi-select field Tripbits. In my database I have Blogs, Tripbits and Blog_Tripbits tables. When inserting a new blog I need the blog to post and then the multi selected tripbits to post to the Blog_Tripbits table with the blog_id and the tripbit_id (value from each multi selected item). I know I can get the blog_id and then use a repeater in the server connect but I can’t figure out how to get the array value of the multi-select Tripbits field to the repeat.

Thanks.