amazing!
i wish i could understand whats behind this formula...
i mean, why "1" as the match value?
and why do you add 0 to the index array?
In...
=MATCH(1,INDEX((A3:T3<>"")+0,1,0),0)
The INDEX((A3:T3<>"")+0,1,0) bit unfolds something like this:
INDEX({FALSE,FALSE,TRUE,FALSE,...}+0,1,0)
>>
INDEX({0,0,1,0,...},1,0) [ FALSE+0 >> 0; TRUE+0 >> 1 ]
{0,0,1,0,...} stands as it were for a range, 1 for the first row of that range, and 0 for all columns of that range.
The surrounding MATCH picks out the column of the first occurrence of 1 in the foregoing calculated reference. Note that this is still an array-processing formula, but it needs not the control+shift+enter signal because the array is already calculated by the INDEX expression.
For the record, MATCH(TRUE,A3:T3>0,0) is equivalent and requires the array-processing signal.