Problems with Macro window popping up unexpectedly

[Peter621]

I am running excel under office 365 with Windows 10 Enterprise

I am trying to learn how to create a program that will run code automatically (without the use of a button) when a cell's value changes.  I found a tutorial on youtube ( https://www.youtube.com/watch?v=FgT0V4XyxEY ) that did this however when I follow completely I get different results. 

I have created an excel spreadsheet that has a form control button that toggles cell A1 between -1 and +1. The module should change cell C1 Red when it A1 is -1 and Green when A1 is 1.

When I come to run the code to test however I get a Macro window asking me which macro to run as shown below

I have already set the Macro settings in the trust centre correctly (I believe)

The file is saved in a trusted location - can anyone tell me what I'm doing wrong to get rid of this Macro window please?

Thanks in advance for any help

Peter 621

[#2]

@Peter621

If you're running the code with the play button in the VB editor, you have to stay within the sub when pressing play.

The macro begins with:

sub MacroName()

and ends with:
End Sub