Assign unique column names in a loop?

I have a loop that continues to add new columns at the end of a table, until their is no more data, from the source table, to add. However, I'm running into a problem, I can't figure out how to code assigning unique column names within a looping program.

Is there a way to name a column uniquely for each pass through the loop?

I tried the following:

(Setting a declare to equal the date for which the column represents)
declare @date
set @date = (select min(rate_date) from tbl_mastertable)

(But it won't allow me to use the declare as part of the column name.)
select a.*, b.price as 'Column_' + @date

Can anyone help?

Thanks in advance!