將以求吾所大欲也 meaning of 將
i would interpret 將 in that sentence as &quot;in near future&quot; (即將).

抑王興甲兵．危士臣．構怨於諸侯．然後快於心與
王曰．否．吾何快於是．將以求吾所大欲也

mencius challenged 齊宣王, said &quot;or (抑), your majestic (王) increases (興) armours (甲) and soldier (兵), [puts] your officials (士臣) in risk (危), makes up (構) enmities (怨) amongst (於) dukes (諸侯). and then (然後) [you'll be] cheerful (快) in (於) [your] heart (心)?&quot;
his majestic (王) said (曰) &quot;no (否). how come (何) i (吾) [would be] cheerful (快) for (於) these (是)? in near future (將), [these policies are] for (以) seeking (求) my (吾) greatest desire (大欲)&quot;
your translation:

I do (those things) to seek what I greatly desire!

quite good, as a shortcut :)
info added.
well, 齊宣王's greatest desire is in the following text:
https://ctext.org/dictionary.pl?if=gb&amp;id=12913

. . . 欲辟土地．朝秦楚．莅中國而撫四夷也

[your] desire (欲) [is]: open up (辟 --&gt; 開闢) [more] land (土地), [have representatives] in the court (朝 --&gt; 朝廷), from the nation of 秦 and 楚, administrated (莅 --&gt; 蒞) the china (中國), and (而) soothe (撫) all surrounding barbarians (四夷).
at that time (bc 319-301), 齊 is a small nation in 山東半島. then, &quot;中國&quot; is &quot;關中平原&quot;.