Problem with subform

bab

Hi!
i have a problem, and i'm real angry, because i don't know, what i'm doing wrong.
There are 2 tables:

Task Header
1 No. Code20
2. Name Text250
3....

Task Line
1. Task No. Code 20 (Table relation "Task Header")
2. No. Code 20
3. Name Text250
4.....

and 2 forms: a subform (Source table Task Line), and a main form (Sorce table Task Header)

in the main form the subform link property of the subform component is set to "Task No.=FIELD(No.)"

i think thats all.
The problem is, when i'm running the mainform, and want to insert some new line in the subform, the "Task No." field is not filled automatically.
what i'm doing wrong?

bab

i was an idiot...
i didn't defined the Task No., as a key in the "Task Line" table...
sorry, if i was wasting your time