how do I create a trend formula with range that changes
 

I created a trend formula that works, but I want to make the range change as
I add more columns to the source data.

Here is an example:
TREND(B3:X3,B1:X1,Y1,TRUE)
row 3 contains the raw data (cells B3 - X3)
row 1 contains the refrence which is 1 -23

Now I'd run a new raw report and the data would extend to column Y. . . how
do I set up the trend formula so that it automatically changes from B3:X3 to
B3:Y3?