You can reset the paragraph format to bring it back to left aligned
aRow.Range.Style = "Caption"
aRow.Range.ParagraphFormat.Reset

I think your table style (which has defined the paragraphs as centred) is causing the problem you are seeing. I generally try to avoid over-specifying the table styles because they can then override the paragraph styles that I use. Table styles are somewhat problematic because once you have included an 'optional' attribute like font or paragraph format settings, it can be very hard to remove it but easy to reassign.

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Andrew Lockton
Chrysalis Design, Melbourne Australia