Ok guys n gals, so I've found out how to do this. Before you continue any further, understand that you must be rooted and running a custom ROM that supports 4G toggling (i.e. AOKP).

Step 1: Download this app from the Play Store https://play.google.com/store/apps/details?id=com.intangibleobject.securesettings.plu gin&feature=nav_result#?t=W251bGwsMSwxLDMsImNvbS5p bnRhbmdpYmxlb2JqZWN0LnNlY3VyZXNldHRpbmdzLnBsdWdpbi Jd 
Step 2: Open the app, go to Options and scroll down to Custom ROM Actions and ensure that "LTE" is checked
Step 3: Open up Tasker and create a profile entitled 4G On and choose your first context, whether that be battery or whatever else you want to "trigger" 4G to be set as "On."
Step 4: Click New Task at the top of the tasks list and name it 4G On.
Step 5: Click the + button and scroll to Plugins and you will see Secure Settings. Click it.
Step 6: You will see edit configuration; click edit
Step 7: Now you will see a list of the options you have enabled in Secure Settings. We care about 4G, so scroll down to LTE and click it. Then it will ask you what state you want LTE to be in. This is the 4G On profile, so click On. Save and apply the task. 
Step 8: Repeat steps 3-7, but now choose the context you want for 4G to be off, name your profile and task 4G Off, and when you get to the configuration settings in Secure Settings, make sure you check Off for the state of LTE. Save and apply the task.


Now you're done! Make sure to click the checkmark on your profiles screen to ensure that your tasks are enabled

Source