Write 20 rows in first run and next 20 in second run and so on

[Jules22]

I have a wokflow that appends the first 20 rows of input file to output file. I want that in  second run it writes the 21st t 40th row and so on 

[aatalai]

You would need an iterative/batch macro, and use the select records tools

[ScottLewis]

The core of this problem is that you want a value to be different each time the workflow is run.

One way to do this is to store the value you want to change in an external file. Read in a value, use it in the workflow, write out an updated value to the same file at the end. In this case, the value could either be 1,2,3... or 1,21,41... depending on how you want to write the underlying logic. For complex workflows, we will associate a control file with one workflow or set of related workflows to hold things like this. 

[griffinwelsh]

This workflow will work assuming you have a unique key for each record. It checks to see what is in the output file to filter out what has already been written and then writes the 20 highest rows to the output.

[apathetichell]

you would need to read in the output file each time - get a row count - and use the append method in excel. That would determine which record was previously written. FYI - In terms of performance - I cannot see this being considerably faster than recreating the entire file on each run and I can see this being slower if your file is >100k records.