try this:

function asctobin(tnInput)
#define NIBBLES "0000000100100011010001010110011110001001101010111100110111101111"
local lcOutput
lcOutput = substr(NIBBLES, 1 + 4 * bitrshift(bitand(tnInput, 0xf0), 4), 4) + ;
substr(NIBBLES, 1 + 4 * bitand(tnInput, 0xf), 4)
return lcOutput