Lookup Formula - Error multiple values

[Anonymous]

Hi all,

I'm trying to do pull a value out of one table by and matching it to another table where customers both have the same IDs.  Similar to an index match in excel. I'm using the LOOKUP formula and I keep getting an error message.

Basically I need to check that if a customer has been with us for X days that they've had a certain number of appointments. EG: If they're commenced with us for between 6-8 months they need to have had two appointments. Data is sourced from two different tables but will have matching IDs as follows: 

Table 1

IDs   Number_Of_Appointments

Table 2

IDs    Commenced_Days

Currently trying = LOOKUP ( <Table 2 [Commenced_Days]>, <Table 2 [IDs]>, <Table 1 [IDs]) 

But this gives me an error " "A table of multiple values was supplied where a single value was expected" - does anyone know what that means and can fix the error in my formula? 

Thanks

Shivvy

[Zubair_Muhammad · Accepted solution]

@Anonymous 

Give this a shot

Column =
VAR myID = Table1[IDs]
RETURN
    CONCATENATEX (
        CALCULATETABLE ( VALUES ( Table2[Commenced_Days] ), Table2[IDs] = myID ),
        [Commenced_Days],
        ","
    )