Are these the actual names of the Paper sizes in the pc3 file?
The squares in your example file are just the paper sizes. You need to know the Frame layer, and the size range of the Frames that create your viewports. In any case - you should have all the information you need to do it yourself. as I said in the above to lay it out more clearly:
1) You need a range of AREA to be within on the frames. For example, on your "A4x3", (297 x 630) = 187110. Your range for the "square" variable should be a min and max with this value in the middle, such as 187110 - 10000 = 177110 "(> Square 177110)" and 187110 + 10000 = 197110 "(< Square 197110)"
2) each added condition should have the exact name of the Custom paper size:
((and (> Square 177110) (< Square 197110))(vla-put-ConfigName Layout "DWG To PDF.pc3")(vla-put-CanonicalMediaName Layout "_A4x3_(297.00_x_630.00_MM)"))
ALSO:
3) You must have a unique Layer for the Frame polylines or blocks, something like "MyPaperSizeFrameLayer", or anything, as long as it is unique to the frames.