Incorrect random results from formula, why?

[Titian]

Please take a look at the following example. I expect to get in column "C" the last (rightmost) cell along the row, however I am getting random incorrect results often and I don't know why.

Excel Workbook
	C	D	E	F	G	H	I	J	K	L	M	N	O	P	Q
2	Week Number	1	2	3	4	5	6	7	8	9	10	11	12	13	14
3	04.Apr.13	2013	2013	2013	2013	2013	2013	2013	2013	2013	2013	2013	2013	2013	2013
4	Last	04.Jan	11.Jan	18.Jan	25.Jan	01.Feb	08.Feb	15.Feb	22.Feb	01.Mar	08.Mar	15.Mar	22.Mar	29.Mar	05.Apr
5	13.Mar	*	*	*	*	*	*	*	19.Feb	*	*	13.Mar	*	*	*
6	*	*	*	*	*	*	*	*	*	*	*	*	*	*	*
7	*	*	*	*	*	*	*	*	*	*	*	*	*	*	*
8	01.Feb	*	*	*	*	01.Feb	*	*	*	*	*	*	*	*	*
9	*	*	*	*	*	*	*	*	*	*	*	*	*	*	*
10	*	*	*	*	*	*	*	*	*	*	*	*	*	*	*
11	28.Mar	*	*	*	*	*	*	*	*	*	*	*	*	28.Mar	*
12	*	*	*	*	*	*	*	*	*	*	*	*	*	*	*
13	04.Jan	04.Jan	*	*	*	*	*	*	*	*	*	*	*	*	*
14	*	*	*	*	*	*	*	*	*	*	*	*	*	*	*
15	*	*	*	*	*	*	*	*	*	*	*	*	*	*	*
16	22.Jan	02.Jan	*	*	22.Jan	*	*	*	*	*	*	*	*	*	*
17	*	*	*	*	*	*	*	*	*	*	*	*	*	*	*
18	26.Mar	*	*	*	*	*	05.Feb	14.Feb	*	*	*	11.Mar	*	26.Mar	*
19	26.Mar	*	*	*	*	*	*	*	*	*	*	*	*	*	*
Area 4

The formula in cell "C19" is returning the wrong result, it ought to be blank as there are no populated cells to right.
Any help appreciated

 

[Firefly2012]

That's a quite horrible formula for what you are doing - if you are on xl2007+ I would use this:

=IFERROR(LOOKUP(2,1/(D19:Q19<>""),D19:Q19),"")

or perhaps earlier this:

=IF(ISNA(LOOKUP(2,1/(D19:Q19<>""),D19:Q19)),"",LOOKUP(2,1/(D19:Q19<>""),D19:Q19))

 

[Titian]

Thanks Firefly, I'm using 2007 so I have implemented your first formula above.

It works well - thanks for your help.