Select order number from text field

Are there other possible email subject formats?

Are your sales orders always 7 digits?

You could use something like this:

var text string = [Subject];

//If the end of the string is a bracket, take the number from within the brackets
If(Right($String,1)=")",NotRight(NotLeft($String,"("),")")

//Otherwise, take whatever is right of the last space
Right($String," ")

I haven't tested it, but something like that should work.