problem with I/O field in module pool

hi experts,

I am displaying some text in I/O field in module pool screen. I am giving the attributes of I/O field as "output only" type and no input. Initially the input was not enabled for it, only it should be in display mode. Once i click on 'CHANGE' pushbutton then only the input should be enabled and it should be in change mode.will u tell me how to do it programatically.