Need some sed help

[Dazed_75]

I have some C code with lines that look like:
stuff1; stuff2; spPtr+=stuff3; maybesomestuff4

I can find only the lines of interest using grep spPtr+=foo.c but I
wondered if I could easily use sed to convert those lines to
stuff1; spPtr+=stuff3; stuff2; maybesomestuff4

so basically with ; as a delimiter, swapping group 2 and 3 but only for
those lines containing "spPtr+="

Any ideas?

-- 
Dazed_75 a.k.a. Larry

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