All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
If you are asking about the ruling on moving from that job in which you calculate Riba (interest and/or usury), then you must move from it and look for another job that is permissible. You should not give any consideration to your employer, who is asking you to stay in the job, or to the law.
It is not permissible for you, dear questioner, to help in Riba in any form or shape.
Carrying out Riba calculations and reviewing them, is like writing them and witnessing them, and there is an explicit text stating that the one who does so is cursed.
Jaabir narrated that the Prophet said “Allah has cursed the one who consumes Riba (i.e. usury or interest), the one who gives it to others, the one who records it and the one who witnesses it (its transaction).” He added: “All of them are equal in sin.” [Muslim]
"This is an explicit statement that it is forbidden to write the sale contract between the buyer and seller when they deal with Riba, as well as witnessing it, and this Hadeeth is evidence that it is forbidden to help in evil-doing.” [End of quote]
The salary and the money which the one who calculates Riba receives, is considered ill-gotten money and a forbidden earning –we take refuge in Allah from that.
It is not permissible for you to remain in this job except for a necessity or a dire need, in a way that if you leave this job you will not be able to find another job and you fall into destruction, or that you will suffer an unbearable hardship in a way that you will not even sustain the minimum lifestyle of the poor.
If you are asking about the ruling on missing the Maghrib and 'Ishaa' prayers and combining them, then it is not permissible for you to combine them without a sound Islamic excuse, such as travel, illness or rain.
A permissible job, in itself, does not make combining two prayers lawful, let alone the forbidden job.
As for just missing the congregational prayer in the mosque while performing it at its prescribed time, then we hope that there is no sin in that.
Allah knows best.