Expression evaluation error in rule 'apn_uigridtextcolumn'

I am pulling records from a database and would like to format the information in the records. My statement in a rule!APN_uiGridTextColumn:

data: if(filter(fn!isnull,dataSubset.data.projectmanager),"None",touser(dataSubset.data.projectmanager))

returns the ID of the project manager, or "None' if the record is null. What I want to do is convert the ID of the project manager to Last name, First Name, or just last name. But I can't get a user function to work in the statement. A statement like this:

data: if(filter(fn!isnull,dataSubset.data.projectmanager),"None",user(touser(dataSubset.data.projectmanager),"lastName"))

gets me an error message:

There was an error testing the rule:

Expression evaluation error in rule 'apn_uigridtextcolumn' (called by rules 'apn_uipaginggrid' > 'apn_uisectiononecolumn') at function 'user' [line 51]: Error evaluating function 'user' : The passed parameter(s) are of the wrong type.

How can I extract and format data f...

OriginalPostID-101659

OriginalPostID-101659