Using Guides

[gazza]

I have been trying to put together a simple image that will end up 190mm in width using the Guides. I need to place vertical guides 10mm , 25mm, 30mm, and the next 7 at 17mm. I have tried to create a new image the exact length that would be required, and tried to add the guides. I start from the L/H side and all of the guides are measured from the L/H side except I add the additional length each one. When I check with the measuring tool, and when I look at the measurements on the bottom of the screen they are nothing like what I have put in. I have used, Pixels, and MM and CM, but I cannot get this one to work. I have looked for a Tutorial on this, but cannot find one to answer my questiions. This is not the first time this particular task has got me very frustrated. I have also tried using the measuring tool but this does not seem to help. 
Regards
Gazza