Update Current Column Gnumpics By A Numeric Value

I have a table named galleryindex which contains rows of photo gallery names along with an associated id (gsid).

example:
gsid (assigned ID), gnumpics (# of photos), gname (gallery name)
=================
43, 133, our summer visit
493, 53, camping photos

When someone uploads more photos I do the following to recalculate the NEW number of photos for the gallery.

SELECT gnumpics FROM galleryindex where gsid= 43
(select current # of photos from location 43 - our summer visit)
in ASP classic I then do this:
sb = objrs("gnumpics")
sb = sb + totupl
SQL = "UPDATE galleryindex SET gnumpics =" & sb & " where gsid= '" & fnum & "'"

to update the gallery with the new amount of photos which is obtained by pulling the old value into SB, and adding "totupl" (total pics uploaded) to it and then updating the values.In SQL speak it would be like this if 20 photos were just uploaded:

SELECT gnumpics FROM galleryindex where gsid= 43
(results in 133 photos)

UPDATE galleryindex SET gnumpics =153 where gsid= 43
(write back 133 + 20)

Basically I'm trying to update the current column gnumpics by a numeric value and I know there's an easier way then pulling the current, adding to it and then writing it back to SQL.