Auto insert worksheet from template

[Isabelle]

Hi there,

Trying to figure out how to set the automatic insertion of
a worksheet in an invoicing workbook

Ideal scenario:

1) I qualify my clients based on a letter for the type of
invoice (F, C, etc.).

2) I want this letter to be understood as a given template
to be inserted automatically by Excel. If the value is
blank, nothing should be inserted.

3) I want Excel to rename the sheet based on a
calculation, e.g. =sum('sheet'a1)+1

Can anybody help?

Thanks in advance,

Isabelle