I seem to spend a large amount of my time in spreadsheets working on formulas like:
="some text '" & A1 & "', more text: '" & A2 &" etc."
It would be much quicker to use a printf or String.Format string like
=String.Format ("Some text '{0}', more text: '{1}'",A1,A2)
Is there anything like this built in to Excel, or can I call out to CLR?
No, but you can create a naive one simply enough by adding the following to a VBA module:
Public Function printf(ByVal mask As String, ParamArray tokens()) As String
Dim i As Long
For i = 0 To ubound(tokens)
mask = replace$(mask, "{" & i & "}", tokens(i))
Next
printf = mask
End Function
...
=printf("Some text '{0}', more text: '{1}'", A1, A2)