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Your LimeSurvey version: [see right hand bottom of your LimeSurvey admin screen]
Own server or LimeSurvey hosting:
Survey theme/template:
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Hi, I am trying to set up a survey, I have Q1 working where I have a message to show if the user selects option 1 or 2 using {if (Q1_Q1A.code == 'Y' , 'Message displayed.' )}.
Q2 it is a multiple choice, depending on the amount they select I want a different message to appear. Can you help please? I tried using {count(that.Q2.NAOK)>2 , 'New message to appear.'} but it doesn't work. 

Sorry, this is a bit confusing.
1. Why didn't you answer the questions at the start?

2. Where do you want this messages to appear?
As a validation tip?
As a popup or an alert?

So you rerally should send these questions as a lss export to show us what you are trying to achieve.

Best regards
Joffm

Your LimeSurvey version:Version 5.4.5+221010
Own server or LimeSurvey hosting: Own server

Hi, sorry I have exported as lss now. 

I currently have the message appear as a report at the end of the questionnaire. The second message appears all the time, but I would like it to appear when more than 2 options have been ticked in Q2. I hope this makes sense

Hi,
1. Why is Q1 a multiple question if only one answer is allowed?

2. It doesn't work because you didn't do what you said "If the count is >2, then..."
So you have to use an IF statement

{if(count(that.Q2.NAOK)>2 , 'Message 2 to appear','')}

Is it possible to have styling within the 'message 2 to appear' such as a bullet list? I have tried by using <ul> <li> but I get errors with it. 

I have tried by using <ul> <li> but I get errors with it. 

Which errors?
Please, always show us what you did.
We have no crystal ball.

Because I do not see an issue.
 

Joffm