# DLL interface - File name expression

**URL:** <https://forum.plexim.com/t/dll-interface-file-name-expression/753>\
**Category:** PLECS\
**Tags:** code, dll\
**Created:** [March 13, 2020, 11:32am UTC](https://forum.plexim.com/t/dll-interface-file-name-expression/753 "2020-03-13T11:32:13Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Peter\_Maurer](https://avatars.discourse-cdn.com/v4/letter/p/a3d4f5/32.png) [@Peter\_Maurer](https://forum.plexim.com/u/Peter_Maurer)\
**Post date:** [March 13, 2020, 11:32am UTC](https://forum.plexim.com/t/dll-interface-file-name-expression/753/1 "2020-03-13T11:32:13Z")

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Is there a way to specify the file name parameter of the external DLL block as an expression?

Other subsystem masks allow to configure if a string parameter shall be interpreted either as expression or as literal string. I am missing this option for the external DLL interface block. It seems that the string parameter is always interpreted as literal string.

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**Author:** ![Kris\_Eberle](https://dub1.discourse-cdn.com/flex006/user_avatar/forum.plexim.com/kris_eberle/32/6_2.png) [@Kris\_Eberle](https://forum.plexim.com/u/Kris_Eberle)\
**Post date:** [March 13, 2020, 12:00pm UTC](https://forum.plexim.com/t/dll-interface-file-name-expression/753/2 "2020-03-13T12:00:53Z")

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Hello,

No, as the block’s help file says, you must provide the DLL file name directly. PLECS takes certain decisions based on whether or not you include the full path and the file extension.

Regards,  
Kris