Find Last Occurence Of Value And Return Balance From Another Column

I am trying to create a run balance sheet (see attached sheet). Column C has a list of job numbers, with column D showing the reqd quantities. Once the job is run, the qty is entered in column F and either a balance or the word complete returns in column H. My problem is, is that, when a job with a balance attached to it is re-run, that balance should be returned in Column D.

Ie 574361 has a total of 707 of which 320.4 was run, leaving a balance of 386.6.
When I type in 574361 again, I need column D (in the cell next to the job number)to automatically locate the last reported balance and return its value.
I have tried VLOOKUP and INDEX, but cannot get the thing to return.