Change Excel error #N/A to 0 in set ranges, due to no data in database

Excel VBA code to change #N/A to 0 in set ranges does not work. Workbook has a sheet for each day to the month, a button on each that runs macro to get data from a database PI System, based on the date on the sheet. Formula's are set up to pull the data for each hour. Trouble is when there is no data, like when the time changes to DST there is no 24th hour, it inserts error #N/A. Other macro's insert this gathered data at other locations on the sheet, thus #N/A's are carried over. I want to change those #N/A's to 0. My code is supposed to change only those #N/A's, which is set ranges, to values first, then replace them with 0. I don't need to change the first location this data enters the sheet. I have tried different ways & it still doesn't work.

Part of my latest ChangeErrors() Sub is:
Range("C12:Z13").Copy
Range("C12:Z13").PasteSpecial Paste:=xlPasteValues
Range("C12:Z13").Replace What:="#N/A", Replacement:="0"

I have searched the questions that others have asked and found nothing that might help. Please, any suggestions?

I removed my sub ChangeErrors() and tried changing the cell formula's.
Cell BD34 has formula:
{=PISampDat($CM$11,$AF$1,$AF$2,$AG$1,0,)}
Cell BE34 has formula:
{=PISampDat($CM$12,$AF$1,$AF$2,$AG$1,0,)}
Cell BF34 has formula:
{=PISampDat($CM$13,$AF$1,$AF$2,$AG$1,0,)}
In cell BG34 I am able to change the function formula as you recommended to:
=IF(ISERROR(BD34-(BE34+BF34)),0,(BD34-(BE34+BF34)))

Some of the cells that have curly brackets { }, there is a macro that copies that data (24 rows, 1 for each hr., same formula for the 24 hrs.) and transposes to another location on the sheet.
Cells AJ11:AJ34 have:
{=PISampDat($AY$8,$AF$1,$AF$2,$AG$1,0,)}

My Sub EnterMeteredData()
Range("AJ11:AJ35").Copy
Range("C12").PasteSpecial Paste:=xlValues, Transpose:=True

When I tried to change function formula to:
{=IF(ISERROR(PISampDat($AY$8,$AF$1,$AF$2,$AG$1,0,),0,(PISampDat($AY$8,$AF$1,$AF$2,$AG$1,0,))))}
I get error: You've entered too many arguments for this function. When I click OK, the 0 between the comma's is highlighted.
Any suggestion on what I need to do?