These three examples will select the third tab in tab_1. They could be in the script for a CommandButton on the window containing the Tab control tab_1:
tab_1.SelectTab(3)
tab_1.SelectTab(tab_1.uo_3)
string ls_tabpage
ls_tabpage = "uo_3"
tab_1.SelectTab(ls_tabpage)
This example opens an instance of the user object uo_fontsettings as a tab page and selects it: