The sake of a Mitzvah:[1]

It is forbidden to perform professional work [Maaseh Uman] even for the sake of a Mitzvah. [It is however permitted to perform any amateur work [Maaseh Hedyot] for the sake of a Mitzvah.[3]]

_____________________________________

[1] Rama 544:1; Rivash 226; Taz 544:1; See Shemiras Hamoed Kehilchaso chapter 10

Other opinions: Some Poskim rule it is permitted to perform Melacha for the sake of a Mitzvah. [Tosafus, brought in Taz ibid; Tur] It is however unclear if this allowance includes Maaseh Uman. [See Taz ibid who implies even Maaseh Uman is permitted according to Tosafus and Tur; see however P”M 544 M”Z 1 who questions his understanding]

[3] P”M 544 M”Z 1