# 3D Design / 3D Scanning / 3D Modeling > 3D Printing Slicer Discussion >  Simplify3D - Bed probing and print area placeholders - Gcode script

## MicroBond

Hi all,
my printer has a really big bed and often I just need to print small object on different bed areas. So an high-definition probing (with a _BLTouch_) on the whole bed area can result in a useless and really time consuming activity. 

So I'm looking for a way to probe, before each print, only the bed area affected by the print itself. 
To obtain this result I need to set the probing grid in the GCode "_starting script_" using a dynamically composed *M557* command, but at this stage I also need some sort of Simplify3D *variables* in order to "know" the maximum and the minimum X and Y value used in the print process.

Ideally I would obtain something like:


```
M557 X[min_x]:[max_x] Y[min_y]:[max_y]
```

Does _Simplify3D_ provide this kind of placeholders or is obtaining this goal a wild-goose chase?

Thank you!
Luke

P.S. =I'm using Simplify3D v. 4.1.1 + RepRap + Duet

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## sedersmith

Hi buddy, do try inputting with loop variables over the strings. That should work well!Regards,Seder Smith Plex Tutuapp Vidmate

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## equlyhenna

Yes, you can go with sedersmith or find an path which can help you give out things well.On the off chance that anybody is intrigued, my companion and I built up a Cura post handling content (he did the crucial step). I truly figure this would be lucky to be a firmware highlight, similar to I composed a solicitation for. Yet, in the then, for those utilizing Cura: You pass it a solitary boundary (work dividing worth), and it parses the main layer gcode for min/max X and Y directions, and afterward replaces the M557 line in your beginning gcode. LevelingMeshOptimizer.py.txt Simply eliminate the .txt, and drop it here: C:\Program Files\Ultimaker Cura 4.5.0\plugins\PostProcessingPlugin\scripts\ You should have a static work leveling order in your beginning gcode, as: M557 X0:200 Y0:200 S20This, query has been strucking all over, do you think it works out? Let me know with it.

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## MicroBond

Hi equlyhenna,
thank you for your reply and congratulations for your work.
Meanwhile I've discovered that Simplify3D 4.1.2 natively offer the placeholders for the maximum and the minimum X/Y values, so the task has become a breeze. ;-)

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## justinzzz

Hi,
I'm looking for undocumented (custom) placeholders for post-processing scripts. 
By the way, if you need custom Simplify 3D G-Code, there's a good source > Bob's Project Notebook and custom term papers by Bob George.

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