LinkButton control variable and use in VB function

I am new to asp.net/VB and have been trying to make an HTML control (LinkButton or RadioButton) set a variable in the behind code in VB and run in a paging function to display a certain number of items in a datalist.

I can get the radiobutton values assigned to a variable and post back through a Response.Write, but the variable is null within the behind VB code function.  Is there a way to set a global variable to be passed into a VB function created from a radio button submit or linkbutton submit?