formula to lookup formatting and return true false

I apologize if this subject is already a thread out there. I searched, but didn't find anything similar, so I started this one. What I'm looking to do is enter a formula that will look at a cell and determine if it's true or false, based off of the format of the cell rather than the actual entry in the cell. Column C is what I want to evaluate for correct format and the criteria for being true is that the entry needs to be a letter followed by 5 numbers. So on the attached spreadsheet, rows 2-11, 22 and 25 would be false and return and "I" and rows 12-21, 23-24 would be true and return no results (the results would show up in column H). Any help would be greatly appreciated.CB.XLS

Try:

=IF(AND(LEN(C2)=6,ISERR(LEFT(C2,1)+0),ISNUMBER(RIGHT(C2,5)+0)),"","I")

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