Combine 4 pngs from folder into single pdf file, with each layer a different opacity? [SCRIPT?]

Hi All,

I'm hoping someone can help me with this situation.

Here's where I am:

I have a single brown grunge background file.

Then I have 26 other pngs, each representing a letter of the english alphabet, in a hand-drawn style.

I want to generate as many pdf files as possible for all combinations of 3 alphabet letters with the brown in the background.

So for example, the first file could be:

Bottom layer - Brown grunge background - 100% opacity

2nd layer - letter A - 20% opacity

3rd layer - letter B - 60% opacity

4th top layer - letter C - 95% opacity

It will always be the brown grunge png layer as the base layer at 100% opacity, and then a combination of the alphabet letters png files.

I know I can use Microsoft Excel to generate a 3-colum table that can give me all the possible 3-letter combinations of the 26 letters.

If I rename all of my source png alphabet files to match the same data in the excel spreadshet cells,  is there a way to somehow use that excel file to instruct photoshop to do this combining?

If so, how?  I could really appreciate the help.