Not Sure To Use Dsum Or Vlookup For Multiple Searches

I would like to ask recommendations whether to use DSum or Vlookup, in order to do multiple search.

We receive a flat file on a daily basis, which contains four (4) columns. They are Group, Team, Taskname, and Number_of_Employees. The first three columns have text properties and the last one has number property. We copy this sheet into our workbook. There are more than 1,000 rows. I name this tab, "TotalWorkersbyTask".

Each group (first column) has its own tab. We try our best to name each tab to match the name of the first column.

We would like to find the unique value, in order to put the correct Number_Of_Employees into the correct column on each sheet. However, the relationship per column is many to many, which makes it more difficult.

For example,

Group,Team, TaskName, Number_of_Employees

12GR, Robert, Analyze raw data, 2.5
12OV, Tim, Analyze raw data, 1.25
12OV, Bob, Prepare reports, .85
16CJ, Jim, Prepare reports, .50
1008, Mary, Analyze raw data, .25
............

Each tab, such as 12GR, will have the task name on the line "Analyze raw Data" which matches the information "TotalWorkersbyTask" tab.

The problem is, if I do a Vlookup for Taskname only, only the first value of 2.5 will return in to the Number_of_Employees column.

For the tab of group 12GR, the logic supposes to be -> if the group is 12GR, and the name of the task equal to the one appeared in "TotalWorkersbyTask", return me the value of 2.5 in the specific row. With the same logic, on the tab 12OV, the same task name should return me the value of 1.25 as well.

As you see from the example, line 2 and line 3 are the tasks in the same tab, from the flat file received.

Then, this formula can be copied and populated into other rows and other sheets as well.

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Questions:

1. Is there anyway to write the formula to gather the required information? My thought was using the Vlookup. However, it can see only one column.

2. Do I need to rename all the tabs to match the name of the first column received from flat file in order to make it more efficient? (In the present, there are some tabs that match the name, such as 12OV, and some tabs are something like ->Engineering, Research, etc.)