If it's set up as I think you describe (a spreadsheet containing all
the info for a record number along that same row), then simply reverse
the process.

When you write the data to the user form, you've probably got a button
that runs a macro to transfer the data to the cells from your textboxes
such as

Sheets("Data").Cells(14,37).Value = UserForm1.TextBox1.Text (or
similar).

To get the data back to the userform, just reverse the statement and
place it in a suitable event module:

UserForm1.TextBox1.Text = Sheets("Data").Cells(14,37).Value