[NTG-context] button alignment question

Hi, How do you keep the footer buttons between the footer's top and bottom ? \showframe \def\myHeaderButton{\interactionbuttons[width=2cm,height=\headerheight][OK]} \def\myFooterButton{\interactionbuttons[width=2cm,height=\footerheight][OK]} \setupinteraction[state=start] \setupheadertexts[text][aaa][aaa] \setupheadertexts[margin][\myHeaderButton][\myHeaderButton] \setupfootertexts[text][ppp][ppp] \setupfootertexts[margin][\myFooterButton][\myFooterButton] \starttext test \stoptext Thanks, Alan