FM CONVERSION_EXIT_ALPHA_INPUT

HAI EXPERTS,

my requirement is to use this FM CONVERSION_EXIT_ALPHA_INPUT for conversion of input fields.

i have around 6 fields to convert each with different length , i want to use this FM only once to convert all the 6 fields.

CALL FUNCTION 'CONVERSION_EXIT_ALPHA_INPUT'

EXPORTING

input = tablename-fieldname "this part alone i need to input all the fields dynamically

IMPORTING

output = tablename-fieldname. "this part alone i need to input all the fields dynamically

i have to change the input and output names in the fm dynamically.

i need to call this fm in a perform and then change....

can anyone help me on this......