Hi, i am developing a website and i am finding it difficult to come up with a suitable interface to capture 2 timeframes that they user needs to enter into a form.

This is a difficult problem to explain, so apologies if i don't get the message across after one read.

The user has 11 weeks (77 days) to carry out an overall task. Each task comprises of 2 sub tasks (task A and task B). When the user is building the task using the task creation form, they have to choose a timeframe for both task A and task B. The user does not have to use all of the 11 weeks, so they could choose to allocate 1 week to task A and 1 week to task B, however i need some way to show that the choice of one timeframe affects and reflects the choices available for the other timeframe.

For example, if the user chooses a timeframe of 2 weeks for task A, then i need the UI to represent that only 1 - 9 weeks are left for task 2 BUT they do not have to choose all of the 9 weeks... OR if the user chose 5 weeks for task A, then the UI needs to show that only 1-6 weeks are now only available for task B.

The UI must clearly illustrate that both of the timeframes are linked... i do not want to use 2 drop downs where the choice of one reflects the choices available in the other drop down as it will not be obvious to the user that these timeframes are dependent and linked to one another.

Thanks in advance if you for reading this far ;-)