my uncle has a colt border patrol that used to belong to my dad. i know there were very few made, i also know this one has aftermarket grips, a trigger job and an action job.  i would really like to buy it from my uncle so it can be reunited with my dad. does anyone know what it would be worth?

It's basically a Colt Trooper MK III. Barrel is 4" and marked Border Patrol. Depending on condition, $600 to $900 would be ballpark.

There were TWO Colt Border Patrol revolvers.

The first issue was a Colt Official Police with a very heavy 4 inch barrel and exposed ejector rod.  
It was chambered in .38 Special.
Grips were reddish brown plastic, known as "Coltwood". It was made in 1952.
The barrel was marked "Border Patrol" and they had hand stamped USBP stamps and issue numbers on the frame.
There were about 400 made for the US Border Patrol with a VERY TINY few (probably less then 5) sold commercially.
These are very rare guns and bring high prices.
As usual much depends on the condition, and a modified gun would bring less.
Prices depend on the market on an auction but would range from around $500 to over $3000 for a mint version.

The second issue Border Patrol was a Colt Trooper Mark III with a 4 inch barrel.  
It was chambered in .357 Magnum.
It was made from 1970 to 1975.
The barrel was stamped Border Patrol.
It has the Trooper Mark III shrouded barrel and Mark III Target grips.
It was sold as BOTH a US Border Patrol issue gun AND as a commercial sales model.
There were 5,356 with a lesser polished blue finish, and 1,152 in bright nickel.
Official USBP issue models will have hand stamped USBP and issue stamps on the right side of the frame.
Commercial sales models will not have the official issue stamps.
Values again depend on condition and on being in unaltered condition.
For some reason these second issue models aren't yet bringing as high of prices as would be expected.
A blued model will range from $200 to over $900.
A nickel model would be from $300 to over $1,000.
Again, price depends on the market and a official USBP issued gun bringing more.

Both guns can be seen on Coltfever:

http://www.coltfever.com/

And here's a picture to go with the description.

I had one of the MK III's.  It was a PD trade-in.  I liked it quite a bit.  A spring went bad inside it, but it was easy enough to replace.  

A couple of buddies had MK III Troopers, and I decided to be different with the "Border Patrol" marking.  There was absolutely no difference, other than the rollmark on the barrel.  

I'd buy another one, but Colt's are getting expensive.

that does look like it. This specific pistol has more value to me because it was dad's back up in his early days of bustin punks and i want to get it back to my dad.

As above, value depends on the actual condition, whether it's been modified, and whether it has the original grips.
The original box would add value.

It's tough to give values for Colt revolvers due to the skyrocketing prices.
Just as a ball park value, prices will range from a low of $200 for one with little finish, to "over" $900 for one in minty shape.

These prices may be lower or probably higher in a online gun auction.

The Blue Book is the "Bible" for buying and selling guns, but it's always a year behind due to publisher lead time, and Colt prices simply blow past what the Blue Book says.
Here's Blue Book values for a blued Second Issue Colt Border Patrol.  By now prices will be higher
The values are based on the amount of remaining original finish:

60%--$200
70%--$250
80%--$285
90%--$325
95%--$500
98%--$750

As above, these are out of date and values will likely be higher to MUCH higher for a gun in higher condition.