Google-sheets parser for the cell : I got a string in the cell "D1-D4, D8-D11"

Need it calc summ of elenents "D1, D2, D3, D4, D8, D9, D10, D11"

Output - "8"

ps
I can calc summ of "D1, D2,...D11"
but i need the parser for range "D1-D4"