Phrase: "at this rate"

[Attila]

Hi All,

Is the next sentence correct?

I changed the extension and at this rate I could open the file.

[Mister Micawber]

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No; rate implies progress or serial effort. I changed the extension, I retitled it, and I emailed it to myself, but nothing worked. At this rate, I will never get the file open.
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Native English teacher at Mister Micawber's