That's a LOT of code for what you're describing. You cannot return multiple records to a textbox. The closest you can come is to concatenate values, perhaps separating them with commas. However, not only may a listbox be more appropriate, but your whole approach may be kind of wonky. Usually multiple records associate with a single value are represented by a subform in either datasheet or continuous format.
I'll wager you don't have Option Explicit turned on (or at least have it in your module) because you haven't declared strOpLevel (or it isn't obvious that you did). Lastly, please use code tags for anything more than a few lines - see # on thread menu bar.
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.