Issue with Vlookup over 3 sheets

Hi

I am trying to obtain a lookup result using the Vlookup function using 3 sheets of data - Sheet 1 being the parent sheet (where the formula will sit) , Sheet 2 and Sheet 3 being the child (data), however I am unable to find the correct combination.

On the parent (sheet 1) I have one column showing the membership number of our book club i.e Column E MEM12345. I want the adjacent column F on each row to show either that the member has recently joined using the new membership number data from (sheet 2) or is an existing member from the data on (sheet3) by returning the values "New Member" or "Existing Member"

I am familiar in the standard VLOOKUP formula eg. =IF(VLOOKUP(A2,Joined!A:A,1,FALSE),"New Member") to return the value I want using only 1 sheet, however I am unsure on how to combine the same formula that would also reference both sheets to return either values

An example of what I have tried is below, however it is showing an error.

=IF(ISNA(VLOOKUP(A4,Joined!A:A,1,FALSE),"New Member",VLOOKUP(A4,Existing!A:A,1,FALSE),"Existing Member")

Can someone please advise of the correct structure of the formula or an alternative way of acheiving the result?

Regards

Alan