Hi Krishna,
You can implement GET_P_ method of the corresponding attribute of which you want to change the field type at runtime. Try the following code.
CASE iv_property.
WHEN if_bsp_wd_model_setter_getter=>fp_fieldtype.IF condition1. //check your condition here
ev_value = cl_bsp_dlc_view_descriptor=>field_type_input.
ELSEIF condition2. //check your condition here
ev_value = cl_bsp_dlc_view_descriptor=>field_type_picklist.
ENDIF.ENDCASE.
You can check the required conditions and decide the type of the field accordingly.
Thanks & Best Regards,
Leon