Got a tough question about LOOKUP Must be passed a Constant

[MTB-Mik]

So I am know it says if needs to be passed a constant, but I want to be variable constant it there is such a thing.  So I build an action loop that base off of job details put into a form, upon the save the action loop kicks off and creates a row for every part, So I know I could concatenate another value [Main Line Size] and I will if I have to, but I have already work very hard on my table to accommodate this way of coding.  So my question is "Is there any way to pass a variable constant in the lookup function for the Column?"

LOOKUP(CONCATENATE([Number of Manifolds],[Size of Outlet],[Part Count],[SDR]),"Part Count",ID,(IFS([Main Line Size]="20",20,[Main Line Size]="20",20)
))

Function 'LOOKUP' must be passed constant values for its tableName, lookupColumn, and returnColumn parameters: LOOKUP(lookupValue, tableName, lookupColumn, returnColumn). Consider wrapping the constant parameters in double quotes to ensure correct parsing.

This works but not with as much control as i  want, 20 is my column name

LOOKUP(CONCATENATE([Number of Manifolds],[Size of Outlet],[Part Count],[SDR]),"Part Count",ID,20)

[dbaum · Accepted solution]

IFS(

[Main Line Size] = "20", 
LOOKUP(CONCATENATE([Number of Manifolds],[Size of Outlet],[Part Count],[SDR]),"Part Count","ID","20"), 

[Main Line Size] = "21", 
LOOKUP(CONCATENATE([Number of Manifolds],[Size of Outlet],[Part Count],[SDR]),"Part Count","ID","21"), 

[Main Line Size] = "22", 
LOOKUP(CONCATENATE([Number of Manifolds],[Size of Outlet],[Part Count],[SDR]),"Part Count","ID","22")

)

[Marc_Dillon]

A "variable constant" ! 🤣