Are you writing your data from KNIME to Excel and you would like to write it with currency or you would just like to have currency written in KNIME while having Number type column?
Haven’t tried them yet, but this sounds promising:
Define the text format of you cell (e.g. percent: 0.00% , whole number: #,##0, …). Please use only English locale values, irrespective of your target or local environment.