Adjusting symbology in a layer file

[Kevin_C]

I have a layer file for a geology layer containing attributes for "Age", "Rock Type" and "L_Code". The layer has symbology defined using the "L_Code" attribute. But I want the same symbology applied using the concatenated "Age" and "Rock Type" fields. Each L_Code matches with exactly 1 Rock Type value and 1 Age value. How can I do this? See figures below. 

This is what the original layer file looks like, defined using the L_Code attribute

This is what I want the final legend to look like. The label column shows concatenated strings from both the Age and Rock Type fields.

Thank you for any help!

[JimCousins]

2 choices that I quickly come up with:

1) add a new field to the source and calculate the value based on [Field_1] + " " +[Field_2]

2) using the symbology settings for the layer, choose Categories >> "Unique values, many fields", and choose the 2 fields that are of interest.

Regards,

Jim