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.

I obviously can't grasp your restraints, but why not use a pivot table?

Try this...

Data Range

	A	B	C	D
1		Experiment 1	Experiment 2	Experiment 3
2	Hardness	X		X
3	Solubility		X	X
4	Density	X	X
5
6	Hardness	Experiment 1	Experiment 3

This array formula** entered in B6:

=IFERROR(INDEX($B$1:$D$1,SMALL(IF(INDEX($B$2:$D$4,MATCH($A6,$A$2:$A$4,0),0)="x",COLUMN($B2:$D4)),COLUMNS($B6:B6))-COLUMN($B2)+1),"")

** array formulas need to be entered using the key
combination of CTRL,SHIFT,ENTER (not just ENTER).
Hold down both the CTRL key and the SHIFT key
then hit ENTER.

Copy across to D6.