Multiple Values returned in a lookup

I have a table where the rows are conditions and the columns are experiment numbers, as an example below:

	Experiment 1	Experiment 2	Experiment 3
Hardness	X		X
Solubility		X	X
Density	X	X

The table is fairly large. What I would like to be able to do is use a lookup/formula that will return all the experiment numbers a given condition is tested in. In other words, for a given condition (i.e., Hardness), which columns have an "X". Not sure if that can be done with a lookup or not or if there is another function necessary. I would like to be able to do it without macros though and also have it automatically update if I move the "X" around to different experiments.