Re-sizing disk partitions

I have a 1TB external disk which I had previously divided into two equal partitions. Using Disk Utility I have reduced the size of one of the partitions, but can't enlarge the other partition to take advantage of the now available free space. Both partitions have data on them and I do not wish to erase and start with new partitions. Any way I can enlarge that other partition?

Thanks,
Thom

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