Excel .NET COM – Automation error. The system cannot find the file specified

calendar_today Asked May 19, 2009
thumb_up 11 upvotes
history Updated April 14, 2026

Direct Answer

You need to either invoke regasm with the full path to the assembly as the codebase parameter value or put the assembly into some location which is always on the path for…. This is a prose walkthrough, ranked #70th of 303 by community upvote score, from 2009.


The Problem (Q-score 13, ranked #70th of 303 in the Excel VBA archive)

The scenario as originally posted in 2009

I have a .NET 2.0 COM object that’s used by VBA in Excel. It works fine on my dev machine, but when trying to use it on a clean VM workstation I get this error:

Automation error.
The system cannot find the file specified.

The dll is registered with “regasm /tlb /codebase mycom.dll” and not put in the GAC.
I don’t have administration rights on the VM box

Any ideas?

Why community consensus is tight on this one

Across 303 Excel VBA entries in the archive, the accepted answer here holds solid answer (above median) status — meaning voters are unusually aligned on the right fix.


The Verified Solution — solid answer (above median) (+11)

Verbal answer — walkthrough without a code block

Note: the verified answer is a prose walkthrough. If you need a runnable sample, check Excel VBA entries ranked in the top 10 of the same archive.

You need to either invoke regasm with the full path to the assembly as the codebase parameter value or put the assembly into some location which is always on the path for searching libraries. Otherwise it will not be found when the client tries to instantiate the COM object.


When to Use It — vintage (14+ years old, pre-2013)

Ranked #70th in its category — specialized fit

This pattern sits in the 97% tail relative to the top answer. Reach for it when your scenario closely matches the question title; otherwise browse the Excel VBA archive for a higher-consensus alternative.

What changed between 2009 and 2026

The answer is 17 years old. The Excel VBA object model has been stable across Office 2013, 2016, 2019, 2021, 365, and 2024/2026 LTSC, so the pattern still compiles. Changes that might affect you: 64-bit API declarations (use PtrSafe), blocked macros in downloaded files (Mark-of-the-Web), and the shift toward Office Scripts for web-first workflows.

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Frequently Asked Questions

Is this above-median answer still worth copying?
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Answer score +11 vs the Excel VBA archive median ~4; this entry is solid. The score plus 13 supporting upvotes on the question itself (+13) means the asker and 10 subsequent voters all validated the approach.

The answer has no code block — how do I turn it into a snippet?
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Use the walkthrough above as a checklist, then open a top-10 Excel VBA archive entry for a concrete starting template you can adapt.

This answer is 17 years old. Is it still relevant in 2026?
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Published 2009, which is 17 year(s) before today’s Office 2026 build. The Excel VBA object model has had no breaking changes in that window. Three things to re-test: (1) blocked macros on downloaded files (Mark-of-the-Web), (2) 64-bit API declarations (PtrSafe, LongPtr), (3) any shift toward Office Scripts for web scenarios.

Which Excel VBA pattern ranks just above this one at #69?
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The pattern one rank above is “Meaning of .Cells(.Rows.Count,"A").End(xlUp).row”. If your use case overlaps, compare both before committing.

Data source: Community-verified Q&A snapshot. Q-score 13, Answer-score 11, original post 2009, ranked #70th of 303 in the Excel VBA archive. Last regenerated April 14, 2026.

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