Private methods Importing parameter cannot be changed error

Hi Guys,

I have this scenario where I have a private method inside a class which is having an error "Field SAPMF02K cannot be changed".

here is the code for the private method call.

call method create_bdc_dynpro

importing IM_PROGRAM = 'SAPMF02K'

IM_DYNPRO = '0100'.

code of the method

data: wa_bdcdata type bdcdata.

CLEAR wa_bdcdata.

wa_bdcdata-program = im_program.

wa_bdcdata-dynpro = im_dynpro.

wa_bdcdata-dynbegin = at_true.

APPEND wa_bdcdata to at_bdcdata.

Hope you can help

Thanks!