Photoshop: How to draw a guide with exactly distance with another guide

Before drawing, I want to draw all guides for my layout. For example, I have already guide line named A. After that, I want to have another guide line named B that parallel with guide line A and has distance is 50px.

I have three solutions:

1. Draw line B and by "some way", I can see directly current distance when I'm drawing, so I can make distance exactly as I want.


2. Draw line B. And then I use Ruler tool to see distance between two line. This method has disadvantages: maybe the ruler line that I draw isn't perpendicular with two line A and B and I don't sure when distance is enough.


3. There are other clever ways, that helps me do this job done fast and easily (But I haven't known yet), because I think Photoshop should support this feature.

I have three solutions as above. But I don't know in each solutions, how can I do. Please help me. Thanks :)