Using GREP styles to find all of (x) that doesn't result in (y), & replace with other text

I'm trying to find a way to locate all double spaces (inserted between placeholders in a data merged document) that do not appear at the end of a paragraph line (i.e. that do not result in effectively a soft line break), in paragraphs of text spanning several paragraph lines, and replace said double spaces with "(space)|(space)".

Is this at all possible to achieve using GREP styles & if so, can someone explain how to do so please?

Any help would be very much appreciated. Thanks.