Erratic combo box in vfp grid

Thanks for that, but I think I must be missing something.
I have created a form with 2 unjoined tables in the data environment.
I create a grid based on the 'disputes' table .
I add to one of the columns a combo box drawing from the other table - 'reasons'
When I open the form the grid sorts in the order of an autoinc field (not set as an index field - perhaps I should??)
Just clicking on the combo box of any record seems to resort the grid.
I guess you are suggesting that I need to get the grid sorted properly before I do anything else!
If so, how do I do that, please? there will be many reasons in the 'disputes' table but one in the 'reasons' table
Thanks!

Hi:
I have to leave shortly so this will be left unattended until Monday. THanks for your help so far; I think I am missing something with regard to indexes?
I have looked again at the problem and maybe I have misled you. I have a grid with a combo box. Whenever I click on any record in the grid (except the last) the grid does NOT re-sort; instead the grid scrolls down in a flash  until that record is at the top of the viewable area of the grid. All the records before that record have scrolled upwards,out of view. This occurs even when the contents of the grid do not exceed the length of the grid (so no scrolling required). There is a filter on init of the form; if I remove that the behaviour persists. I will  RTFM and look at indexing at home.......
Then again I may give up and use an array as a combo source!

Hi:
I have sorted the problem.
My form did have the 2 tables joined. Unjoing them stopped the grid resorting.
I also had a field in the that was drawn from the lookup table; when a user clicked the combo and selected a reason from the list, then the field adjacent recorded the description. Taking that field out meant that the drop down list 'stayed drop down' and did not constantly close.
No points!

What was happening is that the record pointer was moving to the last record because of the joining and it was not refreshed. I thought it was an index but it seems from the joining. I think you were using SET FILTER TO.

Thank you very much, CaptainCyril. I do not know if I can do this but I would like to extend the question. Now that I have determined that I should NOT join the lookup table to the main table In the data environment  I  have also had to remove the field that displays in the grid the description from the lookup table. So now I have a grid where a user clicks on a combo to pick a reason code. This code is numeric and, displayed to the user in the grid as a number, useless.  I would like the user to see the description of that reason. But when I do that I get the combo box not staying open! Is there a way of getting the reason to display? I have written a series of if statements that populate the field but it does seem a really awkward way of displaying the text of the reason!