If you want to fill some letters with text and leave others transparent, I can think of two ways.
1) For me the easiest would be to create your text, rasterize and select the letters you want to not have any fill. Use Layer>new>by cut or ctl/cmd + shift + J. Clip your text to the bottom layer as you are doing normally. Then make your other letters a color, such as white that works for your BG, and clip that color to those letters.
Or make two text layers, using the space bar for the missing letters. Oops: this isn't going to work very easily as the letters are different sizes and you'll have to work with the spacing which I think is a pain, but you may not. I'd just rasterize.
2) If you want the letters totally transparent, here is what I would do. Use layer effects and add an outside stroke with color of the stroke being the same as the BG. Rasterize the layer, select the inside color, and mask it out or delete it. If you don't have a colored BG, good luck. Well, you can again apply a stroke, any color that works, probably black given the black text, rasterize and again select the inside color and delete. This will leave a stroke of course, so I don'g know if that will work for you. But I imagine there must be a BG you are going to punch out.
Let me know if this is not clear to you and I'll make a visual aid.
Here is the example of totally transparent letters alongside the filled text. This is in fact a ping, not a jpeg. If you change the appearance of the forum (all the way down this page on the right. There's a drop down menu and dark is a choice, as is fluid or fixed. Try it out on 2 of them and you will see the BG come through. Or you can save as.
Yes, I know it's not carefully completed. You may need to select>modify>expand the clear letters or vice versa on the filled. You might also have to adjust kearning, but this is all a matter of simple tweaking. Or you can use the transform tool.