Display list depending whether cell is blank or not

Hi, I need my worksheet to display a list which, in case any of the columns on the right are not blank, display a list of the headers which containt the non blank cells.

Here is an example;

Header	List	Asia	Africa	N.America	S.America	Europe	Oceania	Antartica
Sales	list1	210		12	41		2

I'd need it to dropdown list1 with the list of headers where there have been sales (Asia, N.America, S.America and Oceania)(Please have into account that my worksheet has 10 thousand rows).

Also, the workbook has 30 sheets with column "K" value being the sale value for that sheet country. Lets say one of the worksheets is called "Italy", I'd like the excel, in case cell "K7" of Italy worksheet is not empty, to add it to a list in a list on cell "B7" on general. Do this for as many worksheets there are, the same for other sales, check cells "K8" and add it to "B8" in general...Hope I was able to explain myself

Any help is welcome, thanks!!