For those who might be curious about the relevance of Excel to Project Euler problems, I am categorizing my solutions. Of the 36 that I have solved, 19 were with Excel or by hand, though some I also solved with VBA. 3 problems were solved using Excel with the UDFs from the Large Number Arithmetic (LNA) module. 5 used VBA and the LNA module. While I solved the remaining 9 with VBA, Excel alone should have been sufficient for at least one (Problem 53, for example).