Function within a function

I am trying to run a Case function within a Case function and I can't get it to work. The function deductible(DDD) runs ok by itself. When I try to run it from dedkind(dedtype) it won't run. I was told that it doesn't have a number to relate to but I don't understand. In dedkind(dedtype) the Case is in T18.

function deductible(DDD) as double
Select case DDD
Case is > 25
deductible = Range("T17")
Case is >=5
deductible = Range ("T17") -5
Case is <5
deductible = 0
End select
End function

Function dedkind(dedtype) as double
Select case dedtype
Case is = "DDD"
dedkind = deductible(DDD)
Case is = "DDD10"
Dedkind = 10
Case is = "DDDIP"
dedkind = 15
End select
End function

In cell AB15 I have =dedkind(t18). T18 has the type of deductible. In cell T17 I have a number that is the amount of deductible. I am new to this and don't understand what a breakpoint is. I think I understand about the undelcred variable but don't know how to correct it. Thanks

In cell AB15 I have =dedkind(t18). T18 has the type of deductible. In cell T17 I have a number that is the amount of deductible. Thanks

I have about twenty types of deductibles and each one has various calculations. I am trying to get the first part working and then I will expand the code. Thanks

I have tried and tried but can't get this to work. Can someone tell me what I am doing wrong and how to correct it. The function Deductible(DXS) runs on its own. When I call it from Dedkind(dedtype) it won't work. I was told I hadn't declared it and have tried but still can't get it to work. Thanks.

Function Deductible(DXS) as double
Select Case DXS
Case is > 25
Deductible = Range("T17")
Case is >= 5
Deductible = (Rang("T17") -5)
Case is <5
Deductible = 0
End Select
End Function


Function Dedkind(dedtype) as Double
Dim Deductible() as Double
Select Case dedtype
Case is "DXS"
Dedkind=deductible(DXS)
Case is "DXT"
Dedkind=10
Case is XST"
Dedkind=15
End Select
End Function