Try using ALT + F10 to open selection task pane, then press F6 and use arrow
keys or Tab key to navigate selection task list and choose the box you want.
Having selected the box then use Shift + F6 to edit the text box.
Hope this helps, if you need more help maybe contact me via email off forum.
Co-ordinator for IT for Visually Impaired
and Additional Learning Support
Sussex Downs College