validation message

Try this: 

a!localVariables(
local!a,
a!textField(
label:"Number Only",
value:local!a,
saveInto: local!a,
validations: if(a!isNullOrEmpty(stripwith(local!a,"0123456789")),"","validation"),
)
)

I have done like this,still it not working,Could you suggest?

 a!textField(
                /*label:"Market Value"*/
                value: rule!CR_FN_setDecimalValues(
                  value_dec: index(fv!item, "marketValue_dec", {}),
                  decPlace_int: 2
                ),
                saveInto: {
                  fv!item.marketValue_dec,
                  a!save(
                    fv!item.discountedValue_int,
                    rule!CR_APP_FN_getDiscountedValueFromMarketValue(
                      crREFCollateral_cdt: local!rowREFCollateral_cdt,
                      marketValue_dec: fv!item.marketValue_dec
                    )
                  )
                },
                readOnly: local!releaseDeleteReadOnlyBool,
                required: rule!CR_APP_FN_requiredConditionsForDocumentaionUnit(
                  crAppSelectedItem_cdt: fv!item,
                  role_txt: ri!role_txt,
                  isRequired_bool: ri!isSecurityCollateralReq_bool
                ),
                validations: {rule!CR_FN_setValueGreaterThanZeroValidation(value_dec: fv!item.marketValue_dec),
                if(a!isNullOrEmpty(stripwith(local!marketValue,"0123456789")),"","Enter a valid number"),
                }
              )

I don't see any values saved to local!marketValue, which you have used in the stripwith function. In case of decimals, add a decimal point also in the with parameter value of stripwith function.

I have defined the local var above

I have defined the local var above