Because I needed to define more than 255 fields for my form, I created 3 tables and used a query to bring them all together. This query is the source of my form, which has a tab control. When I tried to bring up the field list to design my form, it balked saying, "Too many fields defined." My goal is to have all of these fields in one form so that the user has an easier time of entering data. Can I do this, or will I have to resort to creating different forms? I should mention that for one of my forms, I will still have more than 255 fields.

255 Fields, why so many?

Yes, why so many? Could you make use of pop up forms? Flow of data entry IS important, however, the visual effect of the form is likely to be compromised by all those fields. Perhaps your data can be broken down into smaller groups and then a command button could be provided to take them on to the next step in data entry via a secondary or third or even fourth form.

Because each subject that we recruit for our study will be required to make multiple visits within four different time points. During these visits they will fill out multiple forms and take multiple tests, which are unique for the most part. For each form or test, we need to know the date, who gave the test, was the test completed, if it wasn't completed why not, and whether this info was entered into another system (5 pieces of information for each test/form). So what I have on paper is this grid. Tests are listed down the left side of the page and the timepoints and info needed goes across the top of the page. Each cell needs a field. I've set it up so that the tests/forms for each timepoint appear on separate tabbed pages (i.e., there are four tabbed pages on my tab control).

Maybe that is the solution -- to create an individual form for each timepoint, and as suggested add a command button that will take the user to the next timepoint (or form) and skip the tab control altogether. How would I use a pop-up form?

What I really meant to say was simply to have the other form open. You can set the opening form to Modal = yes if you want to keep it on top of other windows until it is closed.

Create a command button on your form using the wizard and have it open another form. If you want to plug in the primary key in the form write something like this on your command button in the code builder.

DoCmd.OpenForm "frmSecondFormName", , , , acFormAdd, , Me.PrimaryKeyName

I would offer that your structure is more of a flat file spreadsheet format. Consider restructuring your table to something as such:


tblTests
TestID
TestName
TestPointInTime

tblTesters
StaffID
StaffName
etc.

tblTestResults
TestID
StaffID
Score1
Score2
Rec_EnteredBy
etc.


I hope that helps a bit.

I hate to gang up on you but restructuring your tables is very important. Simply dividing the columns into n groups and creating 1-to-1 relationships will not solve the problem. The tables need to be normalized if you ever expect to be able to do anything other than simple data entry with them. Here's somereferences to get you started:
http://support.microsoft.com/support/kb/articles/Q288/9/47.ASP
http://support.microsoft.com/support/kb/articles/Q234/2/08.ASP
http://www.microsoft.com/technet/treeview/default.asp?url=/TechNet/prodtechnol/office/plan/sysplan/ureldes.asp
http://www.fmsinc.com/tpapers/genaccess/databasenorm.html
http://www.microsoft.com/technet/treeview/default.asp?url=/TechNet/prodtechnol/office/plan/sysplan/ac101.asp

On the contrary, I don't feel like anyone is ganging up on me. I consider it part of my learning experience. I welcome any suggestions as I am still a novice when it comes to Access and VBA. I am going to the sites that Pat recommended right now.