Merging 2 sheets

I have 2 sheets

1st sheet data

Job_id Host_Name Outcome STEP_INDEX
742762 Blank success Null
742762 QCTCRMBLD07 success 0
742762 QCTCRMBLD02 success 1
742762 Blank skipped 2

2ND sheet data

Job id RunTime QueueTime

742762 52 .4562 0.12365

Now i have to insert the 2nd sheet data into the first sheet whereever the step index is NULL

So Basically my output should be like below:


Job_id Host_Name Outcome STEP_INDEX RunTime QueueTime
742762 BLANK success Null 52 .4562 0.12365 742762 QCTCRMBLD07 success 0
742762 QCTCRMBLD02 success 1
742762 BLANK skipped 2

Attached is my EXCEL SHEET, Please help!