Goals based on amount invoiced.

Hi, I am struggling a little with goals and I was wondering if anyone might help?

I want to create a goal based on a target versus the actual amount invoiced within a time period. So I want to set a target of € 50,000 and have a goal monitor how much is invoiced (before tax) and measure it against that.

Any help would be appreciated, I'm completely lost!

Thanks,

Carl.