发现以前大神留在请款单里的公式

就是将阿拉伯数字转换为中文大写数字。
求个大神解读一下，顺便请教一下我要怎么才能学会这套公式？
谢谢啦。
=IF(ROUND(H15,2)<0,"无效数值",IF(ROUND(H15,2)=0,"零",IF(ROUND(H15,2)<1,"",TEXT(INT(ROUND(H15,2)),"[dbnum2]")&"元")&IF(INT(ROUND(H15,2)*10)-INT(ROUND(H15,2))*10=0,IF(INT(ROUND(H15,2))*(INT(ROUND(H15,2)*100)-INT(ROUND(H15,2)*10)*10)=0,"","零"),TEXT(INT(ROUND(H15,2)*10)-INT(ROUND(H15,2))*10,"[dbnum2]")&"角")&IF((INT(ROUND(H15,2)*100)-INT(ROUND(H15,2)*10)*10)=0,"整",TEXT((INT(ROUND(H15,2)*100)-INT(ROUND(H15,2)*10)*10),"[dbnum2]")&"分")))