RGB and hex >> pantone

its been a day I though it would be a 'take it easy' end to the week, no chance had a whole heap of reports that I thought I had done to re-do. then it was time to match colour.it is funny how everything seems so straight forward until you look in to it. I had been a little bit involved with a project but not much when yesterday I was asked to do some more.
I actually like being busy I really do I enjoy the idea that I have lots of things lined up to do. but what started out looking like it was half an hours colour matching turn in to an awful lot longer.
I had a problem with finding the correct cotton thread for a design (not mine) to be sewn. the image was just a bitmap. the yarn company as most still do work to pantone. so it meant matching a rgb hexadecimal number to a pantone number. I know you can simple pick the pantone colour in photoshop but the colours had been changed manually and already printed on a business card.
the yellow was easy but the blue, a particular two shades were very difficult. it is hard to explain to anyone that a colour on screen is not always, if ever the same as a colour that will be it this case sewn on fabric, (its hard enough when is on paper). I used a couple of sites to help me 1 & 2
hopefully I have got it sorted though I am sure it will come back again.