Try,
1] Go to Formulas | Define Name .
>> Name : Cell_Is_Bold
>> Refers to : =GET.CELL(20,INDIRECT("RC[-1]",0))
2] Use it in helper I2, copied down :
=Cell_Is_Bold
3] In K2, SumBold formula :
=SUMIF(I:I,TRUE,H:H)
p.s. : Get.Cell() is a Excel 4 Macro function, so you need to save file as xlsm or xlsb.
Regards
Bosco