Permutations/Combinations where only certain elements can be re-ordered with certain other elements

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I am sorry if this is posted the wrong sub-forum, but my math knowledge is limited and so I am unsure where else to post.

I am wondering how to calculate the number of possible versions of a series of characters, where only some characters in the series can vary.

5NMB RTTM 8L60 9P7U AJQW 9889

5-N-M-B R/L-T-T-M/N 8-L-6/G-0/O 9-P-7/4-U A-J/3-Q-W/V 9-8/B-8/B-9

Therefore, the following are possible (characters in bold are variations on the original series):

5NMB LTTM 8L60 9P4U AJQW 9889

5NMB RTTM 8L60 9P7U AJQW 9BB9

5NMB LTTN 8LGO 9P4U A3QV 9889

But the following is NOT:

5NMB NTTO 8L60 9P7U ABQB 93V9

  1. How many different combinations are possible where only bold characters can vary and they can vary only with the bold character that follows them with a "/"? Is there a formula for this? Answered kindly by JMoravitz.
  2. How would I go about generating all these different combinations using excel or similar software?

I hope this makes sense. I have attached a picture of this question formatted in a way which might be clearer

I am new to the forum so forgive me if my posting etiquette or anything is off-point-- and please let me know so my posts are better in the future!

I look forward to your responses.

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Note that only nine places of your sequence can vary that too only with 2 choices. The other letters need not to be permuted.

Hence for each of these places there are two choices to choose from , which will lead to different permutation every time. So using the "product of rule" we get the answer as $2^9=512$