how to filter a list through two filters f->f->display list.

Not sure I follow...I'll take a shot
Got to your list form. click on the column you want to filter. hit f7 and enter your filter value, click ok.
now you list is filtered. now click on the second column you want to filter by. hit f7 and enter your filter value, click ok.

now you list if filtered by two filters.

is this what you mean?

I think what he means is the Job number textbox looks up to the full Job list, and the Task number one looks up to the task list, but filtered by the value of the job number.

If you have the Job number and the Task number as fields in one table, and you set the links correctly, the lookups should work without a problem. If you only have unbound controls on a form then you will have to program the lookup manually.

So I assume that those textboxes are not fields in the source table. The textbox control has a source of a code type variable, that gets set to the Job's "No." field, let's call it JobNo, with datatype Code20. In the Task lookup, you use the value of that variable as a filter in the lookup to the task. The source of that textbox is another variable, let's call it TaskCode, data type Code10. I am writing this off the top of my head, you will need to go into the table design of the tables, and make sure that the variables have the same data type as the fields you want to link to.