MIDI Mapping - Load to active sampler pad

I'm having some difficulty with this. I want to use the "load to active sampler pad" command, however when I map a button to the command I have to enter a value?? This value is obviously dependent on which sample pad is active, so I therefore can't enter any values here as it would always be changing. This command is actually behaving exactly the same as "load to sample pad C/D" where a button is mapped to a given value (sample pad) of 1 - 8. Any help with this will be appreciated. Thanks in advance. 
