Hello Eric.

This application is written in vfp7. The field with a problem is within a grid. It is a regular text box.

You need code like this in a form method that you can call before changing the active page:

IF TYPE( 'Thisform.ActiveControl.name' ) = 'C'
  IF LOWER( Thisform.ActiveControl.BaseClass ) = 'grid'
    FOR EACH loColumn IN Thisform.ActiveControl.Columns
      IF loColumn.ColumnOrder = Thisform.ActiveControl.ActiveColumn
        loControl = EVALUATE( 'loColumn.' + locolumn.CurrentControl )
        loControl.SetFocus()
        EXIT
      ENDIF
    ENDFOR
  ENDIF
ENDIF