Data validation with vba

Question

Normally it is possible to apply data validation in excel through vba but i am having a specific problem

I am using the indirect method for applying validation,normally when i dont use vba i get a warning by excel that "source currently evaluates to an error,do u want to continue?" (this is because cells which indirect refers to may be empty), now i can easily skip this error in excel by clicking "Yes"

Here's the link http://www.contextures.com/xldataval02.html (Dependent validation lists)

But when i try to perform the same thing using vba i am getting a runtime error,there is no friendly prompt which allows me to continue.How can i handle this kind of error.

On error resume isnt working because then vba doesnt apply validation at all.

Here's the code

Set rng = ThisWorkbook.Sheets("input").Range("AB11:AB65536")
With rng.Validation
    .Delete
    .Add Type:=xlValidateList, AlertStyle:=xlValidAlertStop, Operator:= _
    xlBetween, Formula1:= _
    "=INDIRECT(cablecode&""_depth_""&$Q11&""_""&$Z11&""_values"")"
    .IgnoreBlank = True
    .InCellDropdown = True
    .InputTitle = ""
    .ErrorTitle = ""
    .InputMessage = ""
    .ErrorMessage = ""
    .ShowInput = True
    .ShowError = True
End With

cablecode is a static named range

Q11 and Z11 refer to inputs in that particular row

depth and values are normal strings

cablecode can have two values = "is" or "iec"

Q11 can be "xlpe" or "pvc"

Z11 can be "al" or "cu"

since cablecode is constant for whole project ive referred to it directly, Q11 and Z11 can be different for different rows so ive referred to them seperately

The whole string comes out to be "is_depth_al_xlpe_values" similarly different permuations,and all named ranges are already defined

Answer 1

I suppose the following line needs correction from

.Add Type:=xlValidateList, AlertStyle:=xlValidAlertStop, Operator:= _
    xlBetween, Formula1:= _
    "=INDIRECT(cablecode&""_depth_""&$Q11&""_""&$Z11&""_values"")"

to

dim cellToBeReferred as string
cellToBeReferred = cablecode & "_depth_" & Range("$Q11").Value & "_" _
& Range("$Q11").Value & "_values"

.Add Type:=xlValidateList, AlertStyle:=xlValidAlertStop, Operator:= _
    xlBetween, Formula1:= _
    "=INDIRECT(" & cellToBeReferred  & ")"

Taking the string out will help you debug the issue and figure what is the value of named range, you'd want to refer to. See what value cellToBeReferred results into and correct the concatenation using above.

EDIT after reading OPs comment

In that case, surround the INDIRECT with ISERROR and give a dummy cell reference. For e.g.

"=IFERROR(INDIRECT(" & cellToBeReferred  & "), Z1)"

Where Z1 is a cell to be referred if INDIRECT fails.