DOSBOX and the mapper for nokia n900

hello javispedro,
i´m german and i have a nokia n900 with the us-keyboard.
dosbox is a great tool for me, for i have programmed a lot of software in clipper 87.

the programs are running fine, but there is one problem with the keymapper.
the keymapper is neccessary for me, because all programs need the function keys and the esc-key.
i have rover.sys us in the autoexec and it works fine.
when i have mapped for example the esc-key with :
add
backspace
hold
that the backspace-key with ctrl-key is the replacement for the esc-key
it works only for one time in the application.
when i push the key once again, esc is no longer on the key.
thats with all other function-keys the same.

what can i do ?

kind regards
michael