Need help with applying a condition to a form

[Derek]

I followed directions, but I am new to Access, and not
sure what VBA means. I went into the control window for
the afterupdate, and to codes. I imputed the code, but I
keep getting a else without if response. I am also in the
Private sub after update window. I am not sure if that is
the correct procedure. There are two choices in the field
that I am trying to condition. One I would want to allow
to update subsequent fields, and the other to block update
to subsequent fields. I am also getting a debugger
response when I try to see if the condition has been
applied. All the info from what I have in terms of
literature does not mention how to do it, and I
desperately need help.