Hi ghawton,
You can accomplish this using conditional formatting. I recommend that you watch the video at the bottom of the article so that you first understand what conditional formatting is and how to implement it. Once you have done this, you can create your own formatting rules that apply formatting when the condition is true.
If the condition of the rule is based on data from a line item, you will need to make sure that you select the Data Member Invoice.InvoiceLine.Invoice in your rule. Then, if you want to check if the Item Name is ‘Consulting Service’ for example, you can use the condition editor to create the following rule:
[Item] == 'Consulting Service'
Give this a shot and let me know if you have any other questions.
I hope this helps.
-Audisho