[Limdep Nlogit List] Error 1097: Unusable LHS variable in choice model setup

[Jason Ong]

I am doing a preliminary analysis on a DCE and am trying to run a MNL model
using NLOGIT 6
But I came across this error - "Error   1097: Unusable LHS variable in
choice model setup"
I am not sure what I am doing wrong with my code (data set also attached as
*.csv file)

NLOGIT
; Lhs = ChoiceV, cset, altij
; Choices = A,B,C
; Model:
U(A,B)=prep1*prep1+prep2*prep2+condom*condom+sex1*sex1+sex2*sex2+test1*test1+test2*test2+pep*pep/
U(C)=neither
$

thanks for your help.

*Jason Ong*