Need help with the correct expression to calculate based on column types

[Tiger1]

I need help writing the expression to calculate (sum) a row:

I need:

If “Column Type” = “Sales/Invoice” [Current Trx Amount] - [Current Trx Amount] (if the “Column Type” is “Credit Memos”.

Here is what i currently have (It is a TRAIN wreck - I know!!!):

IFS( [Document Type] = “Sales / Invoices”,

[Current Trx Amount] - IFS( [Document Type] = “Credit Memos”, [Current Trx Amount])
)
)

Here is the table (example) showing the raw data i need to calculate:

Thanks