Update 1:
Because my question is not clear, so I post second example

Because row
I assume that when you say "column header" you really mean "row header".
Considering that the first cell (containing the text "Column Header") is at A1 this is the formula you have to introduce in cell A2:
=IF(B2>0, $B$1, IF(C2>0, $C$1, IF(D2>0, $D$1, "")))
Drag this formula down on as many rows as you need and it'll (hopefully) achieve what you want.