[AccessD] A2003:Replacing 'tokens' in a string

Hi team

Assuming the string below

"[AccountNo]=1234","[InvoiceNo]=1234567","[InvoiceDate]=04/01/2010","[Name]=
Barry"

How would I get just the Invoice Number bit = Eg 1234567?

The 'token' [InvoiceNo] will be constant followed by an "=" sign

But sadly the position of the [InvoiceNo] token in the string will not be
constant - Otherwise I'd just use MID()

Nor will the length of the invoice number - Some may be 4 digits others 6
etc

I need to pull just the Invoice Number (And the Account Number) out of the
string to build a new string being used elsewhere

Many thanks in advance

Darren