Set unitName="water"
Set unitQuantity=43
Set text to "I want " & unitQuantity & " units of " & unitName
If you load these lines of text from csv, it may be easier to put tags in them and then use replace expression.
You can mark tags with some rarely used symbol - #$@%& etc.
For example, CSV file contains this string:
"I want #quantity# units of #name#"
And then you do:
Set text to replace(textFromCSV, "#quantity#", str(unitQuantity))
Set text to replace(textFromCSV, "#name#", unitName)