2 variables in lookup

hey folks

hope someone can help, I used my zoho creator application out in the field on my iphone for the first time today and I am very happy with the results. My Swimming Pool Management solution is fairly basic so far but I'm hoping to develop it (with a lot of help from people on this forum!!!!) so that it is more in line with what I'm trying to achieve.

... I digress...

I have 3 forms; customers, pools, pool care records.

In my 'pools' form I have a 'Pool Address' field and a 'Day of Service' field.

In my 'pool care records' form I have a lookup to the 'pool address' field in the 'pools' form, this allows me to record test results for this particular pool.

However, I need to sort the 'Pool Address' by the 'Day of Service' on the pool care records form.

Let me illustrate:

On Monday I have 20 pools to visit
On Tuesday I have 15 pools to visit
On Wednesday I have 30 pools to visit

---> as it stands the lookup field would have 65 addresses to scroll through! Can someone show or tell me how I can sort these addresses by each day ie. If I select Monday, the lookup will return Monday's addresses; select Tuesday, Tuesdays addresses, etc.

I hope this is clear, thank you for any help

regards

Steven B