sql - TSQL - running total -

i have script i'm trying work out running balance on set of transactions:

so key fields here opening balance. balance of when report run. value same each "accountid" in query.

the total value value of transaction has taken place. (no column name) row number resets after each new account finds in result set -

row_number()over(partition accountid order postingdate) 

what doing in balance field want following.

when row number = 1, use opening balance , add total value. can see doing fine.

however, struggling achieve each subsequent row, how calculate balance on line below it.

so in example above first row shows balance of 125.80. want 2nd row 226.98. balance + total value rows not have row number of 1.

select balance = openingbalance +          sum(totalvalue) on (partition accountid                               order postingdate                               rows between unbounded preceding , current row)    t; 

the rows between limits sum rows prior 1 in sort order, otherwise sum include rows in partition.

rows between unnecessary in case.

more on window functions.