Put Variables In URL

I am trying to put variables in this URL which is related to yahoo finance :

.Name="hp?s=NVDA&a=00&b=31&c=2001&d=11&e=29&f=2006&g=m&y=0"

I defined at the beginning

Dim start_date As Date
Dim end_date As Date
Dim datestring As Variant
start_date = #1/31/2001#
end_date = #11/26/2006#
and put them in datestring

I passed the datestring to a new sub which has the URL:

.Name="hp?s=NVDA&a=00&b=31&c=2001&d=11&e=29&f=2006&g=m&y=0"

So, my question is, i tried to put the (1/31/2001) and (26/11/2007) which is in the above URL which is separated in variables and the URL remain the same