Joint account issue

We are several months away from a Final Hearing. Their is a joint account that requires approval of both parties. One of the parties needs to access funds in the joint account to pay their rent and significant child related expenses, while the other will not approve the withdrawals. Does the party that needs the funds have any legal recourse apart from mediation and waiting for the outcome of the Final Hearing?

How long has the account required both parties approval?
How long is it since income was paid into the account?
How has rent been paid until now?
What are the child related expenses, is it essentials or nice to haves?

Thanks for responding WYSSPECIAL

The account has needed both parties approval since inception (over 10 years ago), there have been no withdrawals the funds have sat untouched.

It has been over 10 years since funds were paid into the account.

The rent has been paid from other bank accounts in my sole name but which have now been considerably depleted

Child expenses are in dispute as they are school fees which on one hand is a nice to have on the other hand a considerable amount of written evidence and reports demonstrate this is a must have for our child. The payment are school fee arrears under a signed contract so we have no option but to pay or continue to incur penalties (and the threat of expulsion prior to the Final Hearing).