Your button has a top-down gradient but it should be easy to do the trick. To get the job done, I'll suggest you to follow these steps:
- obtain a template button, i.e. a button without text.
- modify the template at will, to get button with any kind of text
addressing point 1
Please notice that the gradient of the button is vertical and homogeneous. This really simplify the work: simply, drag a little selection on the left side of the button big enough to cover the height of the text, as shown below
then you have to copy and paste the selection in a new layer (L1). Move the layer L1 to the right (use the arrow key to preserve vertical alignment) to cover the white text, then copy the L1 to a new layer (L2). Now you have another layer to put on the side of L1 to cover another piece of text. Iterate until the text is all covered. Now you can merge all the layers.
addressing point 2
You have your button template! The last thing to do is to add the text. Choose the text tool and position the cursor in the middle of the button to write the new label. I tried to reproduce the shadow effect of the original text by setting an internal shadow with 50% of opacity, 90 degrees direction and 1px of distance.
Here you can find the png template. I did this tutorial in PS for it is the program I have at hand.