If statements for calculating True/False based on two dates

[Javery]

Hello,

I would like to create a field which states True/False using the logic:

If Date1 is within the previous month AND (Date2 is Null OR not within previous month):

True

Else

False

I have been able to create two calculated fields to indicate if the dates are within the previous month but I don't believe this is the correct way to do so. See here (messy expression as date format we are working with is not standard):

If(If(monthstart(Date(Subfield("Custom field (Date)",',',1),'DD/MM/YYYY')) = addmonths(monthstart(today()),-1), 1)=1 and If(monthstart(Date(Subfield("Custom field (Completed Date)",',',1),'DD/MM/YYYY')) = addmonths(monthstart(today()),-1), 1)=0, '1')

Any help greatly appreciated, thank you.

[Or]

If(InMonth(Date1,Today(),-1) and (Isnull(Date2) OR NOT InMonth(Date2,Today(),-1)),True(),False())

I'm not sure if the IsNull() part is even necessary, since null would not be in the previous month, but I included it for ease of reading.