Conditional extract the last sequence number in a userform - Excel VBA

[YantiPrima]

Folks,

I have two columns in "Data Source" sheet. Column B contains of shipment type while column C contains of sequence number.

In column B, consist only of: SS or STS (shipment type)
In column C, consist of:

DT-SS-XXXX if shipment type in column B is SS, and
DT-STS-XXXX if if shipment type in column B is STS

The question is, if I have to add some data thru an userform, with the condition below:
If ComboBox1.value = "SS" then ComboBox2.value will extracting the last sequence number of SS shipment type and if ComboBox1.value = "STS" then ComboBox2.value will extracting the last sequence number of STS shipment type in column C.

Hope that someone could help me. Thank you