scripting - Remove specific lines inside a range with sed -

i'm trying remove block inside pair of matching patterns using sed. given block like:

                            <span  class="fxlbc-t1-x-x-172">m<span  class="small-caps">a</span><span  class="small-caps">r</span><span  class="small-caps">s</span></span>                                <span  class="fxlbc-t1-x-x-248">r<span  class="small-caps">a</span><span  class="small-caps">i</span><span  class="small-caps">s</span><span  class="small-caps">o</span><span  class="small-caps">n</span></span> 

i need remove block:

                            <span  class="fxlbc-t1-x-x-172">m<span  class="small-caps">a</span><span  class="small-caps">r</span><span  class="small-caps">s</span></span> 

i'm trying in sed. first problem i'm hitting when using n selector, problem of odd vs lines. i've fixed doing this:

sed -i 'n  /.*<span \nclass="fxlbc-t1-x-x-172".*/,/.*class="fxlbc-t1-x-x-248".*/ {    /.*fxlbc-t1-x-x-172.*/d    }' test.html  # add empty line sed -i '1i\ ' test.html  sed -i 'n  /.*<span \nclass="fxlbc-t1-x-x-172".*/,/.*class="fxlbc-t1-x-x-248".*/ {    /.*fxlbc-t1-x-x-172.*/d,    /.*    }' test.html 

i'm pretty sure there must easier way of doing it, , i'm stuck how remove other lines of block (without removing fxlbc-t1-x-x-248 span line). idea?

i given answer problem colleague:

sed -i ':a ; $! { n ; ba } ; $s/\(<span\( \|\n\|\t\)\+class="fxlbc-t1-x-x-172">[^4]\+\)\(<span\( \|\n\|\t\)\+class="fxlbc-t1-x-x-248">\)/\3/g' test.html 

it puts whole file in buffer, , standard search , replace on buffered string. reckon it's ugly though, trick.