formula assist

Hi Dears,

Could you please assist regarding the below formula as i have additional condition 

=IFS(G$2<=EOMONTH($B18,-1)+1,$D18*Assum!$C$9,G$2>EOMONTH($B18,Assum!$K$9-1)+1-EOMONTH($B18,-1)+1,0,MOD(MONTH(G$2)-MONTH($B18),3)=0,$D18*Assum!$E$9/Assum!$J$9,TRUE,0)

after the first result i need to add a result ofAssum!$D$9 if it including a % and the rest will devided as per the formula

Thanks