=SUMIFS('April 18'!S:S,'April 18'!M:M,Summary!A:A,'April 18'!O:O,"4.2018")+SUMIFS('May 18'!T:T,'May 18'!N:N,Summary!A:A,'May 18'!P:P,"4.2018")+SUMIFS('July 18'!$U:$U,'July 18'!$N:$N,Summary!$A:$A,'July 18'!$Q:$Q,"4.2018")+SUMIFS('June 18'!$U:$U,'June 18'!$N:$N,Summary!$A:$A,'June 18'!$Q:$Q,"4.2018")

Function IndLevl(cell As Range)

    Application.Volatile
    IndLevl = cell.IndentLevel

End Function

=IF(IndLevl(G3)>0,"",SUMIFS($C:$C,$A:$A,F3,$B:$B,1.2))