How can we write BDC program to upload data in to line items(VA01) ?

Error in processing BDC table control program...

How can i populate data through bdc program dynamically, when some of the lines are in disable mode....

for e.g ...

in va01 transaction code ....

1 to 5 lines are not in disable mode....

but 5 to 10 lines are in disable mode...

so hw u process those remaining disable lines at runtime and populate data in to the fields of line items...through bdc program..