[Tim]

-- function to reposition editbox

local function RepositionEditBox(self)

   if not self then return end

   local name = self:GetName()
   local box = _G[name.."EditBox"]
   box:ClearAllPoints()
   box:SetPoint("BOTTOM", self, "TOP", 0, 22)
   box:SetPoint("LEFT", self, -5, 0)
   box:SetPoint("RIGHT", self, 10, 0)

end


-- code to initiate the repositioning

for i = 1, NUM_CHAT_WINDOWS do
   RepositionEditBox(_G["ChatFrame"..i])
end

To change the positioning of the box you will want to edit the 1st SetPoint.

BOTTOM = anchor point (so in that line you're anchoring the bottom of the editbox)
self = the chatframe (if you want to anchor it to a different parent then you will need to change all 3 setpoints)
TOP = relative point (basically where you want to position said object in reference to "self" or the parent)
0 = x coords
22 = y coords