The following code gives an integer answer representing
minutes:

For Each C In .Range("B5:AF310")
With C
.NumberFormat = "0"
.Value = (Range("A" & C.Row).Value * 60) / _
(Cells(3, C.Column).Value / 60)
.Value = Round(C.Value, 0)
End With
Next

Problem: when the value is 59, I cannot find a 'nice' way to display as
hours and minutes (eg 62 should display
as 1:02)

but I am using this:
If .Value 59 And .Value < 120 Then
i = .Value - 60
If i < 10 Then
.NumberFormat = "General"
strA = "1:0" & i
C.Value = strA
Else
.NumberFormat = "General"
strA = "1:" & i
C.Value = strA
End If
End If

Is there a better way, please?

Regards.