Isn't there an more straightforward way to deal with Nasdaq requiring "@" and NYSE "U:" before the ticker to request data than this: https://datateamoftheeur.wordpress.com/2016/03/31/us-tickers-to-datastream-mnemonics/
Ok, do something like this in Excel, its simple, straightforward.... You need to for example repetively add U: prior to each stock code. In cell A1 type in U: In cell B1 type in your stock code, eg F for Ford. In cell C1 type in formula: =CONCATENATE(A$1,B1) [don't forget to use the comma after A$1] You only need U: only in cell A1 by using $ in formula. There you've now stitched them together. You can stitch numerous cells just by extending the cell formulas. Copy cell formula down for all your different stock codes. Because cells in column C are formula cells, you can convert to text only by highlighting all you C column formula cells, go Ctrl + C (copy) then paste using Ctrl + Shift + V Either Ctrl + shift + V in same column will overright your formulas, or if you wish to keep formulas, then paste in a different column.