SSRS report that outputs the number of invoiced lines with a group by

Question

I've never used SSRS before so I'm not too familiar with its capabilities. I need to make a report that is grouped by Division Code, and then counts the number of invoices that are the same (by Invoice Number), and displays that in a column (I called it Invoice Lines). I'm trying to get something that looks like this:

And this is what I have so far, I know that the Invoice Lines value should be an expression, though I am not sure what expression to use or how to get it to work. When I created the report, I put all the fields in the details section and the Division Code in the group by section using the report wizard, but I'm not sure if that's right either as its not displaying anything when previewed:

Image added of trying count expression from comment:

Answer 1

If you have grouped it by invoice number, then just an =count(Fields!Invoice_no.Value) should do the trick. Just ensure that this expression is on the grouped column header and not on the details line itself.