Change fill color of all dependent cells when value changes

The title says it all. I have a cell range with 5 possible entries and need the backgrounds color coded to these entries. Some entries are dependant on other entries, so the change of one cell would effect others. It is very simple in design:

P = Yellow
T = Green
X = Gray
F = Dark Green
R = Red

For individual modification I have it set-up with:

Private Sub Worksheet_Change(ByVal Target As Range)
    Dim icolor As Integer
    If Not Intersect(Target, Range("E4:Q37, S4:W37, Y4:AF37, AH4:AO37")) Is Nothing Then
        Select Case Target
            Case "R", "r"
                fcolor = 1
                icolor = 3
            Case "F", "f"
                fcolor = 2
                icolor = 10
            Case "T", "t"
                fcolor = 1
                icolor = 43
            Case "P", "p"
                fcolor = 1
                icolor = 6
            Case "X", "x"
                fcolor = 2
                icolor = 16
            Case Else
                fcolor = 1
                icolor = 0
        End Select
        Target.Value = UCase(Target.Value)
        Target.Font.Bold = True
        Target.Font.ColorIndex = fcolor
        Target.Interior.ColorIndex = icolor
    End If
End Sub

When I enter a P in one cell it will change another cell to a T, requiring both cells to be recolored, but this script only seems to do one cell. To make it simple, I'd like it to update the entire cell range based upon the individual cell contents whenever any single cell is modified.

Any ideas?

Re: Change fill color of all dependent cells when value changes

Quote from AAE;512539

Run your code in the worksheet_calculate event.

My apologies but I don't know how I would have to modify the code for that. I know the opening of the code, but simply changing that didn't do anything cept make it error.