One way would be to have the store number entered from a combo box.

Have a table of all your store numbers, locations, etc. Make a combo box based off that table and add in all the fields that are needed for the autofilling. For the properties of the combo box, only have it display the column of data for the store number. In the text boxes that you want auto filled on the form, enter this as the control source:

=[Combo Box Name].[Column](1)

or

=[Combo Box Name].[Column](2)

and so on to display the other columns of data from the combo box.

That is how I have done it in the past. Good luck.

Can you give more details about the location of the fields you are referring to?

From your original post, I was thinking that you had two forms:
1) Store form - This form allows you to edit the Region # and store name of a store
2) Second form - This form has a record source of a table that contains a field to track the store id. The form also has two additional fields to lookup the region # and store name from the store table.

Are you trying to update the region # and store name from the second field? If so, that won't work directly; some vba would be needed.

Are you trying to update the region # and store name from the store form? If so, then it should work; we will need to investigate further into the situation.

Lastly, if you have the second form open and then update the store info on the store form while the second form is open, then the second form will need see the updates until you close and reopen it unless you requery the form.