If this is in C1, then you can just double-click the fill handle,
which is the small black square in the botton right corner of the
cursor. This will copy it down as far as you need it, assuming the
data is contiguous in column B (no Blanks).

Hope this helps.

Pete

On Dec 18, 4:59*pm, Dylan @ UAFC
wrote:
Can't get this to work right.
got about 300000 rows

just need to considate
=a1&"_"&b1 *(need to have the _)
of course when I crtl + shift + enter
it copies the same form all the way down

shortcut advise plese