Need help with variables and conditionals

Cliffy

Forgive the possibly dumb question, but I've been slamming my head against this for a week now.
I'm trying to make IPP generate 2 rolls from the same table, then if the first and second roll are the same, replace the second with a different value.
here is my test code

Set: B=[@Roll&;#93;
Set: A=[@Roll&;#93;
[when] {$A} = {$B} [do] [B==Carter] [end]
Table: MyTable
{$A} {$B}
Table: Roll
Allen
Bradley

and here are the only unique outputs

Allen Allen
Allen Bradley
Bradley Allen
Bradley Bradley

Never Allen Carter or Bradley Carter. I've read and re-read the help files on variables and conditionals so much that they've lost all their meaning. I'm sure this is not an impossible task, but I'm stumped. I've imagined a couple of possible workarounds, but I really want to learn how to do variables and conditionals right.
Thanks in advance!
-Cliffy

Ed_NBOS

I think you just want a deck pick. See the write up in the help file.

Table: Main
[!MyName] [!MyName]

Table: MyName
Allen
Bradley
Carter

Cliffy

Sorry, I think that my example code muddied the problem. Allen, Bradley, and Carter were supposed to be stand-ins for A, B, and C. I'll explain the actual context this time.
The generator is for Gamma World 2010 characters. The way you make a character is to roll for a primary and secondary origin, both from the same table. If you roll the same entry for both, then your secondary becomes "Engineered Human" instead (this is the only way to get the engineered human origin).

The origin table has 20 entries (which is why I truncated the example), so when I run the genny I get a lot of "Android Cockroach" and "Felinoid Speedster", but every now and then I get "Yeti Yeti". Engineered human never occurs.

Here is the actual code

Set: Primary=[@Origin&;#93;
Set: Secondary=[@Origin&;#93;
[when] {$Primary} = {$Secondary} [do] [Secondary==Engineered Human] [end]
Table: Simple Gamma World Character
{$Primary} {$Secondary}
Table: Origin
Android
Cockroach
Doppleganger
Electrokinetic
Empath
Felinoid
Giant
Gravity Controller
Hawkoid
Hypercognitive
Mind Breaker
Mind Coercer
Plant
Pyrokinetic
Radioactive
Rat Swarm
Seismic
Speedster
Telekinetic
Yeti
EndTable:

Sorry for the confusion, but hopefully the problem makes more sense now.

Ed_NBOS

The problem is you are putting the [when] on its own line, so it will get ignored. A [when] is part of an expression. So you need to put it someplace where it will be evaluated - in this case, in the Set statement. Use a temporary variable to hold the value you want to check:

Table: Main
Set: Primary=[@Origin&;#93;
Set: a=[@Origin&;#93;
Set: Secondary=[when] {$a} = {$Primary} [do]Engineered Human[else]{$a}[end]
{$Primary} / {$Secondary} 

Table: Origin
Android
Cockroach
Doppleganger
Electrokinetic

which outputs:

Android / Electrokinetic 
Cockroach / Engineered Human 
Doppleganger / Cockroach 
Cockroach / Android 
Cockroach / Doppleganger

Cliffy

Thanks, that explains a lot!