I'm afraid the specific information you are looking for is to all intents and purposes impossible. A man's company and platoon are almost without exception not found on his service record and his record anyway has not survived the WW2 bombing that destroyed 60% or so of WW1 records.
The war diary for the battalion also, as was normal, names none of the rank and file that became casualties.
Given the distance of about 100 miles between Trones Wood and the hospitals in Rouen, it is highly likely that he was wounded some time before the 11 July. The battalion sustained 75 casualties on 1 July, 30 on 2 July and was heavily shelled on 3 July, sustaining about 75 wounded during the day. There were some 53 casualties between then and the 16th. I would suggest that the action in the first days of July is most likely the place/time that he was wounded and the location(s) can be established.
Do you have access to the war diary on Ancestry? The May to August period can be downloaded for £3.50 from the National Archives:
http://discovery.nationalarchives.gov.uk/details/r/C14054580MaxD
PS The Liverpool Museum may have material on 4th Pals.
https://www.amazon.co.uk/Liverpool-Pals-Service-Battalions-Regiment/dp/1844156419 may help in general. I couldn't find any 4th Pals web site.