I have one categorical independent variable and one interval dependent variable. I want to determine if there is any association between the two. Is correlation appropriate? If so, which correlation (Pearson, spearman, others?) and which of these is associated with the CORREL function in Excel. How do I do it in excel?
Hi and welcome. It depends. If your independent variable is binary, then yes, it makes sort of sense to use the Pearson correlation (which is also called a point-biserial correlation). Depending on what you want, a t-test might make more sense. See the thread here. CORREL is the function you want.

If your independent variable is non-binary and nominal, then correlation makes no sense. See here.

A categorical variable is a nominal variable. But if you meant an ordinal variable, then you can do a Spearman's correlation. Excel doesn't have a built-in function, but since Spearman is just Pearson with ranks, you can do it this way.
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