Macro: Updating data meeting conditions or adding new if not found

Hi all,
I'm trying to solve this issue for a week now. My code is totaly massed up, so I deleted all of it and want to start from the scratch again.
I basically got 2 files: 1 import/source file and 1 target file.
Both files have the columns Date, ID, Test, Purpose, Status.
When updating the target file, the macro is supposed to only consider entries in the source file with a specific Purpose. For those entries, the macro must then check if the source file's data is already in the target file by considering Date, ID and Test (so basically Date, ID and Test create a unique identifier).
If the entries do exist in the target file, only the status in the target file should be updated.
All entries not found should be added at the bottum of the target file.
There are a couple of solutions for this issue in the web, tried reproducing them, w/o success.
Do you have an idea how to handle this?
Thanks a lot in advance!!!

Can you post copies of both files? De-sensitize the data if necessary.

Sorry for the delay. I was having problems with my computer. Your target file has "#N/A" in some cells in column D. The "#N/A" has to be replaced with an actual value or with a zero. This macro will replace them with zero's.

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Place this macro in a standard module in the "target" workbook and then with both workbooks open, run the macro:

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Change the file name (in red) and the sheet names (in blue) to suit your needs.

Thanks a million, Mumps1!!! Amazing how swift and fast this macro works!
2 last questions:
a) If I only want to check for the source file's lines with "Purpose 4" how do I need to integrate that?
Enlarging

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with the additional column "Purpose" (I assume this is done by changing

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to

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and adding

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after

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yields a out of range error.
b) How do I update number of columns and their order? What do I need to change in the code? I.e. the source file has 26 columns with B = ID, C = Date, K = Test, M = Status and R = Purpose, whereas the target file has 18 columns with E = Date, F = Test, H = ID and I = Status.
If new entries are added to the target file, the following columns of the source file need to be copied to the target file: S to A, T to B, F to C, C to E, K to F, R to G, B to H, M to I.
Once again: thanks a lot for your support!

Please attach a version of the 2 files with the additional columns and explain in detail what you want to do.

Try:

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You are very welcome.