This is just an opinion, but I would advise you to stick with VBA for your standard development using Excel. Using .NET is definitely the next step, but it greatly simplifies Excel development.
Using .NET has many advantages, mainly regarding strong typing, but VBA has huge advantages over .NET when it comes to deployment. VBA is also a simpler language to start with, especially for working with Excel, which has many members that do not have typical return values.
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